[AD] dmc unicode patch

["Matthew Leverton" <meffer@xxxxxxxxxx>]

As far as I can tell, DMC's C runtime does not support unicode
filenames. Attached are patches to prevent DMC from trying to call the
unicode routines.

Previously Allegro was defining the IS_OLD_WINDOWS macro at runtime to
true if the version of Windows was older than 2000. The macro was only
being used to detect unicode support. I've replaced the macro with a
new, more descriptive internal variable _al_win_unicode_filenames that
is set at runtime.

* aintern.h: removed IS_OLD_WINDOWS.
* aintwin.h: removed IS_OLD_WINDOWS and added AL_VAR(int,
_al_win_unicode_filenames)
* wfile.c: replaced IS_OLD_WINDOWS with !_al_win_unicode_filenames
* wsystem.c: sets _al_win_unicode_filenames at runtime. (Hardcoded to
FALSE for DMC.)

Tested under MinGW and DMC on both Vista and Windows 98.

--
Matthew Leverton

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