Original commit message from CVS:
* ext/ogg/gstoggdemux.c: (gst_ogg_pad_submit_page),
(gst_ogg_demux_get_prev_page), (gst_ogg_demux_perform_seek),
(gst_ogg_demux_handle_page), (gst_ogg_demux_chain),
(gst_ogg_demux_loop_forward), (gst_ogg_demux_loop_reverse),
(gst_ogg_demux_loop):
Implement first stab at reverse playback.