Now that we have `appname', make much wider use of it. In

particular, the config box uses it in place of the word `PuTTY',
which means mid-session reconfig in pterm will look less strange
once I implement it. Also, while I'm at it, I've personalised all
the dialog boxes and menu items and suchlike so that PuTTYtel
actually claims to be PuTTYtel rather than PuTTY.

[originally from svn r3074]