This will let us put two controls side by side (e.g. in disjoint
columns of a multi-col layout) and indicate that instead of the
default behaviour of aligning their top edges, their centreline (or,
even better if available, font baseline) should be aligned.

NFC: nothing uses this yet.

The number of people has been steadily increasing who read our source
code with an editor that thinks tab stops are 4 spaces apart, as
opposed to the traditional tty-derived 8 that the PuTTY code expects.

So I've been wondering for ages about just fixing it, and switching to
a spaces-only policy throughout the code. And I recently found out
about 'git blame -w', which should make this change not too disruptive
for the purposes of source-control archaeology; so perhaps now is the
time.

While I'm at it, I've also taken the opportunity to remove all the
trailing spaces from source lines (on the basis that git dislikes
them, and is the only thing that seems to have a strong opinion one
way or the other).
    
Apologies to anyone downstream of this code who has complicated patch
sets to rebase past this change. I don't intend it to be needed again.

If you select an entry in the saved sessions list box, but without
double-clicking to actually load it, and then you hit OK, the config-
box code will automatically load it. That just saves one click in a
common situation.

But in order to load that session, the config-box system first has to
ask the list-box control _which_ session is selected. On Windows, this
causes an assertion failure if the user has switched away from the
Session panel to some other panel of the config box, because when the
list box isn't on screen, its Windows control object is actually
destroyed.

I think a sensible answer is that we shouldn't be doing that implicit
load behaviour in any case if the list box isn't _visible_: silently
loading and launching a session someone selected a lot of UI actions
ago wasn't really the point. So now I make that behaviour only happen
when the list box (i.e. the Session panel) _is_ visible. That should
prevent the assertion failure on Windows, but the UI effect is cross-
platform, applying even on GTK where the control objects for invisible
panels persist and so the assertion failure didn't happen. I think
it's a reasonable UI change to make globally.

In order to implement it, I've had to invent a new query function so
that config.c can tell whether a given control is visible. In order to
do that on GTK, I had to give each control a pointer to the 'selparam'
structure describing its config-box pane, so that query function could
check it against the current one - and in order to do _that_, I had to
first arrange that those 'selparam' structures have stable addresses
from the moment they're first created, which meant adding a layer of
indirection so that the array of them in the top-level dlgparam
structure is now an array of _pointers_ rather than of actual structs.
(That way, realloc half way through config box creation can't
invalidate the important pointer values.)

The idea of these is that they centralise the common idiom along the
lines of

   if (logical_array_len >= physical_array_size) {
       physical_array_size = logical_array_len * 5 / 4 + 256;
       array = sresize(array, physical_array_size, ElementType);
   }

which happens at a zillion call sites throughout this code base, with
different random choices of the geometric factor and additive
constant, sometimes forgetting them completely, and generally doing a
lot of repeated work.

The new macro sgrowarray(array,size,n) has the semantics: here are the
array pointer and its physical size for you to modify, now please
ensure that the nth element exists, so I can write into it. And
sgrowarrayn(array,size,n,m) is the same except that it ensures that
the array has size at least n+m (so sgrowarray is just the special
case where m=1).

Now that this is a single centralised implementation that will be used
everywhere, I've also gone to more effort in the implementation, with
careful overflow checks that would have been painful to put at all the
previous call sites.

This commit also switches over every use of sresize(), apart from a
few where I really didn't think it would gain anything. A consequence
of that is that a lot of array-size variables have to have their types
changed to size_t, because the macros require that (they address-take
the size to pass to the underlying function).

My normal habit these days, in new code, is to treat int and bool as
_almost_ completely separate types. I'm still willing to use C's
implicit test for zero on an integer (e.g. 'if (!blob.len)' is fine,
no need to spell it out as blob.len != 0), but generally, if a
variable is going to be conceptually a boolean, I like to declare it
bool and assign to it using 'true' or 'false' rather than 0 or 1.

PuTTY is an exception, because it predates the C99 bool, and I've
stuck to its existing coding style even when adding new code to it.
But it's been annoying me more and more, so now that I've decided C99
bool is an acceptable thing to require from our toolchain in the first
place, here's a quite thorough trawl through the source doing
'boolification'. Many variables and function parameters are now typed
as bool rather than int; many assignments of 0 or 1 to those variables
are now spelled 'true' or 'false'.

I managed this thorough conversion with the help of a custom clang
plugin that I wrote to trawl the AST and apply heuristics to point out
where things might want changing. So I've even managed to do a decent
job on parts of the code I haven't looked at in years!

To make the plugin's work easier, I pushed platform front ends
generally in the direction of using standard 'bool' in preference to
platform-specific boolean types like Windows BOOL or GTK's gboolean;
I've left the platform booleans in places they _have_ to be for the
platform APIs to work right, but variables only used by my own code
have been converted wherever I found them.

In a few places there are int values that look very like booleans in
_most_ of the places they're used, but have a rarely-used third value,
or a distinction between different nonzero values that most users
don't care about. In these cases, I've _removed_ uses of 'true' and
'false' for the return values, to emphasise that there's something
more subtle going on than a simple boolean answer:
 - the 'multisel' field in dialog.h's list box structure, for which
   the GTK front end in particular recognises a difference between 1
   and 2 but nearly everything else treats as boolean
 - the 'urgent' parameter to plug_receive, where 1 vs 2 tells you
   something about the specific location of the urgent pointer, but
   most clients only care about 0 vs 'something nonzero'
 - the return value of wc_match, where -1 indicates a syntax error in
   the wildcard.
 - the return values from SSH-1 RSA-key loading functions, which use
   -1 for 'wrong passphrase' and 0 for all other failures (so any
   caller which already knows it's not loading an _encrypted private_
   key can treat them as boolean)
 - term->esc_query, and the 'query' parameter in toggle_mode in
   terminal.c, which _usually_ hold 0 for ESC[123h or 1 for ESC[?123h,
   but can also hold -1 for some other intervening character that we
   don't support.

In a few places there's an integer that I haven't turned into a bool
even though it really _can_ only take values 0 or 1 (and, as above,
tried to make the call sites consistent in not calling those values
true and false), on the grounds that I thought it would make it more
confusing to imply that the 0 value was in some sense 'negative' or
bad and the 1 positive or good:
 - the return value of plug_accepting uses the POSIXish convention of
   0=success and nonzero=error; I think if I made it bool then I'd
   also want to reverse its sense, and that's a job for a separate
   piece of work.
 - the 'screen' parameter to lineptr() in terminal.c, where 0 and 1
   represent the default and alternate screens. There's no obvious
   reason why one of those should be considered 'true' or 'positive'
   or 'success' - they're just indices - so I've left it as int.

ssh_scp_recv had particularly confusing semantics for its previous int
return value: its call sites used '<= 0' to check for error, but it
never actually returned a negative number, just 0 or 1. Now the
function and its call sites agree that it's a bool.

In a couple of places I've renamed variables called 'ret', because I
don't like that name any more - it's unclear whether it means the
return value (in preparation) for the _containing_ function or the
return value received from a subroutine call, and occasionally I've
accidentally used the same variable for both and introduced a bug. So
where one of those got in my way, I've renamed it to 'toret' or 'retd'
(the latter short for 'returned') in line with my usual modern
practice, but I haven't done a thorough job of finding all of them.

Finally, one amusing side effect of doing this is that I've had to
separate quite a few chained assignments. It used to be perfectly fine
to write 'a = b = c = TRUE' when a,b,c were int and TRUE was just a
the 'true' defined by stdbool.h, that idiom provokes a warning from
gcc: 'suggest parentheses around assignment used as truth value'!

This commit includes <stdbool.h> from defs.h and deletes my
traditional definitions of TRUE and FALSE, but other than that, it's a
100% mechanical search-and-replace transforming all uses of TRUE and
FALSE into the C99-standardised lowercase spellings.

No actual types are changed in this commit; that will come next. This
is just getting the noise out of the way, so that subsequent commits
can have a higher proportion of signal.

This continues my ongoing crusade against dangerous 'void *'
parameters.

ATOFFSET in dialog.h became obsolete when the old 'struct Config' gave
way to the new Conf, because its only use was to identify fields in
struct Config for the generic control handlers to update.

And lenof in ssh.h is redundant because there's also a copy in misc.h.
(Which is already included _everywhere_ that lenof is used - I didn't
even need to add any instances of #include "misc.h" after removing the
copy in ssh.h.)

The last use of it, to store the contents of the saved session name
edit box, was removed nearly two years ago in svn r9923 and replaced
by ctrl_alloc_with_free. The mechanism has been unused ever since
then, and I suspect any further uses of it would be a bad idea for the
same reasons, so let's get rid of it.

(cherry picked from commit 42c592c4)

Having found a lot of unfixed constness issues in recent development,
I thought perhaps it was time to get proactive, so I compiled the
whole codebase with -Wwrite-strings. That turned up a huge load of
const problems, which I've fixed in this commit: the Unix build now
goes cleanly through with -Wwrite-strings, and the Windows build is as
close as I could get it (there are some lingering issues due to
occasional Windows API functions like AcquireCredentialsHandle not
having the right constness).

Notable fallout beyond the purely mechanical changing of types:
 - the stuff saved by cmdline_save_param() is now explicitly
   dupstr()ed, and freed in cmdline_run_saved.
 - I couldn't make both string arguments to cmdline_process_param()
   const, because it intentionally writes to one of them in the case
   where it's the argument to -pw (in the vain hope of being at least
   slightly friendly to 'ps'), so elsewhere I had to temporarily
   dupstr() something for the sake of passing it to that function
 - I had to invent a silly parallel version of const_cmp() so I could
   pass const string literals in to lookup functions.
 - stripslashes() in pscp.c and psftp.c has the annoying strchr nature

The last use of it, to store the contents of the saved session name
edit box, was removed nearly two years ago in svn r9923 and replaced
by ctrl_alloc_with_free. The mechanism has been unused ever since
then, and I suspect any further uses of it would be a bad idea for the
same reasons, so let's get rid of it.

I'm about to add a list box which expects to contain some very long
but uninformative strings, and which is also quite vertically squashed
so there's not much room for a horizontal scroll bar to appear in it.
So here's an option in the list box specification structure which
causes the constructed GTKTreeView to use the 'ellipsize' option for
all its cell renderers, i.e. too-long strings are truncated with an
ellipsis.

Windows needs no change, because its list boxes already work this way.

[originally from svn r10219]

custom free function, in case you need to ctrl_alloc a structure which
then has additional dynamically allocated things dangling off it.

[originally from svn r9922]

length limit, just as I did to FontSpec yesterday.

[originally from svn r9316]

allocated type.

The main reason for this is to stop it from taking up a fixed large
amount of space in every 'struct value' subunion in conf.c, although
that makes little difference so far because Filename is still doing
the same thing (and is therefore next on my list). However, the
removal of its arbitrary length limit is not to be sneezed at.

[originally from svn r9314]

'Config' in putty.h, which stores all PuTTY's settings and includes an
arbitrary length limit on every single one of those settings which is
stored in string form. In place of it is 'Conf', an opaque data type
everywhere outside the new file conf.c, which stores a list of (key,
value) pairs in which every key contains an integer identifying a
configuration setting, and for some of those integers the key also
contains extra parts (so that, for instance, CONF_environmt is a
string-to-string mapping). Everywhere that a Config was previously
used, a Conf is now; everywhere there was a Config structure copy,
conf_copy() is called; every lookup, adjustment, load and save
operation on a Config has been rewritten; and there's a mechanism for
serialising a Conf into a binary blob and back for use with Duplicate
Session.

User-visible effects of this change _should_ be minimal, though I
don't doubt I've introduced one or two bugs here and there which will
eventually be found. The _intended_ visible effects of this change are
that all arbitrary limits on configuration strings and lists (e.g.
limit on number of port forwardings) should now disappear; that list
boxes in the configuration will now be displayed in a sorted order
rather than the arbitrary order in which they were added to the list
(since the underlying data structure is now a sorted tree234 rather
than an ad-hoc comma-separated string); and one more specific change,
which is that local and dynamic port forwardings on the same port
number are now mutually exclusive in the configuration (putting 'D' in
the key rather than the value was a mistake in the first place).

One other reorganisation as a result of this is that I've moved all
the dialog.c standard handlers (dlg_stdeditbox_handler and friends)
out into config.c, because I can't really justify calling them generic
any more. When they took a pointer to an arbitrary structure type and
the offset of a field within that structure, they were independent of
whether that structure was a Config or something completely different,
but now they really do expect to talk to a Conf, which can _only_ be
used for PuTTY configuration, so I've renamed them all things like
conf_editbox_handler and moved them out of the nominally independent
dialog-box management module into the PuTTY-specific config.c.

[originally from svn r9214]

GtkTreeView, GtkComboBox and GtkComboBoxEntry instead of the various
old deprecated stuff. Immediate benefit: GTK2 natively supports real
drag lists, hooray!

[originally from svn r7959]

in place of making a network connection. This has involved a couple
of minor infrastructure changes:
 - New dlg_label_change() function in the dialog.h interface, which
   alters the label on a control. Only used, at present, to switch
   the Host Name and Port boxes into Serial Line and Speed, which
   means that any platform not implementing serial connections (i.e.
   currently all but Windows) does not need to actually do anything
   in this function. Yet.
 - New small piece of infrastructure: cfg_launchable() determines
   whether a Config structure describes a session ready to be
   launched. This was previously determined by seeing if it had a
   non-empty host name, but it has to check the serial line as well
   so there's a centralised function for it. I haven't gone through
   all front ends and arranged for this function to be used
   everywhere it needs to be; so far I've only checked Windows.
 - Similarly, cfg_dest() returns the destination of a connection
   (host name or serial line) in a text format suitable for putting
   into messages such as `Unable to connect to %s'.

[originally from svn r6815]

contents, and doesn't automatically maintain scroll position at the
bottom when new entries are added while the list is open, but it's a
start.

[originally from svn r3087]

name was, not to put too fine a point on it, wrong.

[originally from svn r2997]

Buttons now have an `iscancel' flag to go with `isdefault';
dlg_last_focused() now explicitly passes the control it _doesn't_
care about (`I want the last control that had focus and isn't this
one'); and in the GTK implementation, various fixes have happened,
notably including arrow keys working sensibly in list boxes and the
treeview and short font aliases being expanded correctly to
initialise the font selectors.

[originally from svn r2958]

them.  This is useful for compilers that warn about un-prototyped functions.

[originally from svn r2952]

in the portable dialog interface. This has allowed me to remove
`ssd->savedsession' in config.c, which was (I believe) the only
out-of-place piece of per-instance data in the dialog template
stuff. Now we should actually be able to run more than one config
box in the same process at the same time (for platforms that'll find
that useful).

[originally from svn r2925]

to pieces, and put it back together in a new table-driven form.
config.c sets up a data structure describing most of the config box;
wincfg.c adds in the Windows-specific options (so that config.c can
also form the basis for Mac and Unix config boxes). Then winctrls.c
contains a shiny new layout engine which consumes that data
structure, and windlg.c passes all WM_COMMAND and similar messages
to a driver alongside that layout engine. In the process I've sorted
out nicer-looking panel titles and finally fixed the list-boxes-are-
never-the-right-size bug (turned out to be Windows's fault, of
course). I _believe_ it should do everything the old config box did,
including context help. Now everyone has to test it thoroughly...

[originally from svn r2908]