use lagrange multipler instead of qp for ratecontrol, this may break some things, tell me ASAP if u notice anything broken
quality which was 1..31 float is now a 1..FF_LAMBDA_MAX int, and FF_QP2LAMBDA * qp can be used to convert to the new range

Originally committed as revision 2348 to svn://svn.ffmpeg.org/ffmpeg/trunk