[AD] windowed mode patch

["Isaac Cruz" <icruzbal@xxxxxxxxxx>]

Changes:

- fixed 15 vs 16 bit modes (in windowed mode):
If video card doesn't support 16 bit modes, and the user try
set_color_depth(16) with desktop at 15 bit, set_gfx_mode() will fail (if the
desktop is at any other depth, it will use software conversion). 15 bit mode
will only work if desktop is at 15 bit (using hardware blitting)

- move all asm code to "update.s".  I have tested it only with MSVC, but it
should work with any compiler.

- added more software conversion. So far:
  16 to 32 bits
  32 to 16 bits
  32 to 15 bits
  8 to 15 bits
  8 to 16 bits
  8 to 32 bits

- to apply the pach, extract it to allegro/ directory and run
"patch -p1 < window.diff"
Also you have to make depends because there's a new file "update.s"

TODO:
- Clip window in software conversion.
- Dirty update.
- Fix bugs :)

Attachment: window.zip
Description: Zip compressed data