[MPlayer-dev-eng] new rgb2rgb stuff

[Nick Kurshev]

Hello!

I've perform changes to replace old rgb15to16mmx stuff with new one from postproc subfolder.
I've found that modified by me files also can be modified for using MMX, MMX2, 3DNOW optimized
versions of rgb24to32 and rgb32to24.
So if their author still participate with mplayer then let they'll perform corresponded changes.
(Simply I have no possibility to test every vo driver).