ext/vorbis/vorbisdec.*: Vorbis streams can be embedded in other container formats than ogg, container formats where t...

Original commit message from CVS:
* ext/vorbis/vorbisdec.c: (vorbis_dec_sink_event),
(vorbis_handle_data_packet), (vorbis_dec_chain),
(vorbis_dec_change_state):
* ext/vorbis/vorbisdec.h:
Vorbis streams can be embedded in other container formats
than ogg, container formats where the demuxer might set
timestamps on encoded vorbis buffers instead of those silly
granulepos thingies. In short: make vorbisdec handle
timestamps on incoming buffers as well.