ext/dvdread/dvdreadsrc.c: Allow and implement non-flushing and/or segment seek (mainl...

ext/dvdread/dvdreadsrc.c: Allow and implement non-flushing and/or segment seek (mainly in TIME and chapter format).

Original commit message from CVS:
* ext/dvdread/dvdreadsrc.c: (gst_dvd_read_src_read),
(gst_dvd_read_src_create), (gst_dvd_read_src_handle_seek_event):
Allow and implement non-flushing and/or segment seek
(mainly in TIME and chapter format).
* gst/mpegstream/gstdvddemux.c: (gst_dvd_demux_process_event),
(gst_dvd_demux_get_subpicture_stream),
(gst_dvd_demux_synchronise_pads),
(gst_dvd_demux_sync_stream_to_time):
* gst/mpegstream/gstmpegdemux.c: (gst_mpeg_demux_process_event),
(gst_mpeg_demux_send_subbuffer),
(gst_mpeg_demux_sync_stream_to_time),
(gst_mpeg_streams_reset_cur_ts):
* gst/mpegstream/gstmpegdemux.h:
* gst/mpegstream/gstmpegparse.c: (gst_mpeg_parse_process_event),
(gst_mpeg_parse_pad_added), (gst_mpeg_parse_handle_src_query):
Delegate a query to upstream if it can't be handled.
Make segment stop aware.
Fix (subtitle) stream synchronization.
Add some debug statements.