3dnow version of the Horizontal & Vertical Lowpass filters
mmx version of the Horizontal Default filter
mmx2 & C versions of a simple filter described in a paper from ramkishor & karan
added mode flags & quality2mode function


git-svn-id: file:///var/local/repositories/mplayer/trunk/postproc@2160 b3059339-0415-0410-9bf9-f77b7e298cf2