Vorbisfile could get itself into an uninitialized state if there is a
hole in the audio data right after a valid set of headers.  Changed
process_packet to keep going without complaint if a hole is found;
later we'll need to revert this to returning (and properly handling)
the 'hole' flag, but there are currently no more detailed error codes
than '-1'.

Monty

svn path=/trunk/vorbis/; revision=546