Remove hardcoded reference to libvorbis version, as this is usually wrong.
Need a libvorbis call to get a version string (such as the vendor string).
Update documentation in --help message to:
 - fix badly wrong documentation of -b
 - document the --managed option
 - document the -v option
 - clean up documentation of a few other related options.


svn path=/trunk/vorbis-tools/; revision=9021