ext/ogg/gstoggdemux.c: Faster seeking.

ext/ogg/gstoggdemux.c: Faster seeking.

Original commit message from CVS:
* ext/ogg/gstoggdemux.c: (gst_ogg_demux_src_query),
(gst_ogg_demux_src_event), (gst_ogg_pad_populate),
(_read_bos_process), (gst_ogg_demux_iterate), (gst_ogg_pad_new):
Faster seeking.
* ext/theora/theoradec.c: (theora_dec_sink_convert):
Time-to-default conversion.
* ext/vorbis/vorbisdec.c: (vorbis_dec_chain):
Don't error on unknown packets, just skip. We should probably
read them if we want to support chained ogg.