ext/vorbis/vorbisdec.*: Delay sending events (newsegment, tags) until the decoder is properly initialized.

Original commit message from CVS:
* ext/vorbis/vorbisdec.c: (gst_vorbis_dec_init),
(gst_vorbis_dec_reset), (vorbis_dec_sink_event),
(vorbis_handle_comment_packet), (vorbis_handle_type_packet):
* ext/vorbis/vorbisdec.h:
Delay sending events (newsegment, tags) until the decoder is properly
initialized.
Fixes #347295