rewrote quantizer
 fixed bias (+10% compression/quality for h263 like codecs)
 qscale=1 support
 mpeg1 intra frames looks far less blocky
added codec_id field


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@423 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b