LAME (Lame Aint an MP3 Encoder) Code (SVN)

of ms_ratio of both granules. New formula uses ms_ratio from both
granules and the previous and next granule. This will help avoid toggleing
MS stereo off for a single frame. Long runs of MS stereo or regular
stereo will not be affected.

also fixed a bug in frame analyzer - it was accessing l3_xmin in the last
scalefactor (l3_xmin and maskings are not computed for last scalefactor)