gst/rtp/: Flush adapter on disconts.

gst/rtp/: Flush adapter on disconts.

Original commit message from CVS:
* gst/rtp/gstasteriskh263.h:
* gst/rtp/gstrtph263pdepay.c: (gst_rtp_h263p_depay_process),
(gst_rtp_h263p_depay_change_state):
* gst/rtp/gstrtph263pdepay.h:
* gst/rtp/gstrtph264depay.c: (gst_rtp_h264_depay_class_init),
(gst_rtp_h264_depay_setcaps), (gst_rtp_h264_depay_process),
(gst_rtp_h264_depay_change_state):
* gst/rtp/gstrtph264depay.h:
* gst/rtp/gstrtpmp4adepay.c: (gst_rtp_mp4a_depay_class_init),
(gst_rtp_mp4a_depay_setcaps), (gst_rtp_mp4a_depay_process):
* gst/rtp/gstrtpmp4gdepay.c: (gst_rtp_mp4g_depay_process):
Flush adapter on disconts.