gst/udp/gstmultiudpsink.*: Add qos-dscp property to manage the Quality of service.

gst/udp/gstmultiudpsink.*: Add qos-dscp property to manage the Quality of service.

Original commit message from CVS:
Patch by: Henrik Eriksson <henriken at axis dot com>
* gst/udp/gstmultiudpsink.c: (gst_multiudpsink_class_init),
(gst_multiudpsink_init), (gst_multiudpsink_setup_qos_dscp),
(gst_multiudpsink_set_property), (gst_multiudpsink_get_property),
(gst_multiudpsink_init_send), (gst_multiudpsink_add_internal):
* gst/udp/gstmultiudpsink.h:
Add qos-dscp property to manage the Quality of service.