Another try at fixing swscale on win64, as per r31153.
Don't change paramater passing, but instead use casts.
Shouldn't affect asm output on anything other than win64.
libswscale should work on win64 now.
The rest of ffmpeg still isn't win64 compatible due to the issue of xmm
clobbers, but swscale doesn't use any SSE.
Patch by Anton Mitrofanov <BugMaster AT narod DOT ru>.
Originally committed as revision 31751 to svn://svn.mplayerhq.hu/mplayer/trunk/libswscale