h265parse: Copy over DISCONT flag from input buffers

Apply the commit 10ffa08

https://bugzilla.gnome.org/show_bug.cgi?id=754124
diff --git a/gst/videoparsers/gsth265parse.h b/gst/videoparsers/gsth265parse.h
index 91e84ab..d1ab86f 100644
--- a/gst/videoparsers/gsth265parse.h
+++ b/gst/videoparsers/gsth265parse.h
@@ -78,6 +78,8 @@
   GstBuffer *sps_nals[GST_H265_MAX_SPS_COUNT];
   GstBuffer *pps_nals[GST_H265_MAX_PPS_COUNT];
 
+  gboolean discont;
+
   /* frame parsing */
   gint idr_pos, sei_pos;
   gboolean update_caps;