Load the Windows printing subsystem at run time.

The printing functions are split between winspool.drv and spoolss.dll
in a really weird way (who would have guessed that OpenPrinter and
ClosePrinter don't live in the same dynamic library?!), but _neither_
of those counts as a system 'known DLL', so linking against either one
of these at load time is again a potential DLL hijacking vector.