Preliminary work to support the Milan video bios, that will gives access to 24 or 32 bpp modes. I used the svga driver as model to dynamically build video modes list.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%403820