Numerous vorbisfile fixes:

Fixed a seek bug that didn't cause any wrong answers but did have a
minor negative impact on seeking performance

Corrected ov_read_float() prototype ot more closely match how
ov_read() is used.

Rendered all of vorbisfile 64 bit clean for >2GB files.  This required
changing ov_seek_raw(OggVorbis_File *vf,long position) to
ov_seek_raw(OggVorbis_File *vf,ogg_int64_t position).  This breaks lib
compatability for those using this function, please increment the
version number.

Fixed vorbisfile handling of logical streams that begin at a non-zero
PCM offset.  captured live streams, and cut streams, for example, now
behave.

svn path=/trunk/vorbis/; revision=3126