ext/dvdread/dvdreadsrc.c: Don't implement GstBaseSrc::get_size or GstBaseSrc::is_seek...

ext/dvdread/dvdreadsrc.c: Don't implement GstBaseSrc::get_size or GstBaseSrc::is_seekable, otherwise GstBaseSrc will ...

Original commit message from CVS:
* ext/dvdread/dvdreadsrc.c: (gst_dvd_read_src_class_init),
(gst_dvd_read_src_get_size), (gst_dvd_read_src_do_seek),
(gst_dvd_read_src_do_duration_query):
Don't implement GstBaseSrc::get_size or GstBaseSrc::is_seekable,
otherwise GstBaseSrc will think we can operate pull_range based,
which we don't really, and typefinding will fail miserably.
Also, make seeking work somewhat (only works with flumpegdemux
at the moment, mpegstream needs fixing for that first).