removing esp usage

this is certainly not the most beautifull but it should work without -fomit-frame-pointer and PIC and gcc-4 vomits when ebp is given in a constraint directly even with -fomi-frame-pointer so theres not that much choice ...
if anyone knows a simpler/cleaner solution, dont hesitate to suggest it ...

Originally committed as revision 18393 to svn://svn.mplayerhq.hu/mplayer/trunk/postproc