cleanup

remove ugly and slow vertical scaning code
0.1% bitrate increase (foreman@352x288 qp=1)
0.3% bitrate increase (foreman@352x288 qp=8)


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@3353 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b