gst/mpegstream/: Recreate pads on new-media (#160730).

gst/mpegstream/: Recreate pads on new-media (#160730).

Original commit message from CVS:
Reviewed by:  Ronald S. Bultje  <rbultje@ronald.bitfreak.net>
* gst/mpegstream/gstdvddemux.c: (gst_dvd_demux_class_init),
(gst_dvd_demux_handle_discont):
* gst/mpegstream/gstmpegdemux.c: (gst_mpeg_demux_class_init),
(gst_mpeg_demux_handle_discont):
Recreate pads on new-media (#160730).
* gst/mpegstream/gstmpegparse.c: (gst_mpeg_parse_new_pad):
Send discont even if manager changes timestamps (#161929).