ext/theora/theoradec.c: Cleanups, add some G_LIKELY.

ext/theora/theoradec.c: Cleanups, add some G_LIKELY.

Original commit message from CVS:
* ext/theora/theoradec.c: (gst_theora_dec_reset),
(theora_dec_src_query), (theora_dec_src_event),
(theora_dec_sink_event), (theora_handle_comment_packet),
(theora_handle_data_packet), (theora_dec_change_state):
Cleanups, add some G_LIKELY.
Use segment helpers instead of our own wrong code.
Clear queued buffers on seek and READY.
* ext/vorbis/vorbisdec.c: (gst_vorbis_dec_reset),
(vorbis_dec_convert), (vorbis_dec_src_query),
(vorbis_dec_src_event), (vorbis_dec_sink_event),
(vorbis_handle_comment_packet), (vorbis_dec_push),
(vorbis_handle_data_packet), (vorbis_dec_chain),
(vorbis_dec_change_state):
* ext/vorbis/vorbisdec.h:
Remove old useless packetno variable.
Do position query properly.
Add some G_LIKELY.
Do cleanup of queued buffers in new helper function
and use it.