Fixes to command line parsing for quality and bitrate modes.

Valid combinations:

-b  (maps bitrate to VBR q mode)
-b --managed (ABR)
-b -m/-M (implies --managed)
-m/-M with no -q or -b (implies --managaed)
-q
-q -m/-M (implies --managed) for constrained VBR

svn path=/trunk/vorbis-tools/; revision=3600