Open Image Library 1.4.7a Released - Lots of bugfixes

- Fixed a potentially fatal error in ilConvertImage if converting from a palette'd image.
- Fixed ReadProc to take 4 parameters instead of just 3...it was causing problems with iread, which takes two size parameters instead of just one.
- Started preliminary support for 1 and 4-bit .bmp's.
- Fixed 8-bit .bmp loading.
- Rewrote iFreeMem() and a little of ilDeleteImages() in istack.c to fix a rare but very harmful bug when an image isn't loaded completely.
- Added support for more palettes in ilConvertPal().
- Updated png.c to use the new cross-language file-reading. This is the only lib that I could get to use the cross-language stuff for operating on already-opened files.