a few filters (should be removed/merged when arpis videofilter stuff is finished)

-ssf cgb=<float> -> chrominance gaussian blur (nice to improve picture quality)
-ssf lgb=<float> -> luminance gaussian blur (dunno what its good for)
-ssf chs=<int> -> shift chrominance horizontally
-ssf cvs=<int> -> shift chrominance vertically
these will only work if the swscaler is used at all

Originally committed as revision 4295 to svn://svn.mplayerhq.hu/mplayer/trunk/postproc