mpegdemux: accept ID_PRIVATE_STREAM_1 to avoid loosing sync

Current fallback to lost_sync seems to impede a delay to restore
sync. Let the parser parse and skip the private stream.
Here it contains the digital camera brand (in 2010 bytes)
and is repeated twice.

https://bugzilla.gnome.org/show_bug.cgi?id=697283

gst/mpegdemux/gstpesfilter.c

@@ -101,6 +101,7 @@ static gboolean
 gst_pes_filter_is_sync (guint32 sync)
 {
   return ((sync & 0xfffffffc) == 0x000001bc) ||
+      ((sync & 0xfffffffd) == 0x000001bd) ||
       ((sync & 0xffffffe0) == 0x000001c0) ||
       ((sync & 0xfffffff0) == 0x000001f0) ||
       ((sync & 0xfffffff0) == 0x000001e0);