gst/udp/gstudpnetutils.*: Provide a bunch of helper methods to deal with IPv4 and...

gst/udp/gstudpnetutils.*: Provide a bunch of helper methods to deal with IPv4 and IPv6 transparently.

Original commit message from CVS:
Patch by: Bruno Santos <brunof at ua dot pt>
* gst/udp/gstudpnetutils.c: (gst_udp_get_addr),
(gst_udp_join_group), (gst_udp_leave_group),
(gst_udp_is_multicast):
* gst/udp/gstudpnetutils.h:
Provide a bunch of helper methods to deal with IPv4 and IPv6
transparently.
* gst/udp/gstmultiudpsink.c: (gst_multiudpsink_class_init),
(gst_multiudpsink_init), (gst_multiudpsink_set_property),
(gst_multiudpsink_get_property), (join_multicast),
(gst_multiudpsink_init_send), (gst_multiudpsink_add_internal),
(gst_multiudpsink_remove):
* gst/udp/gstmultiudpsink.h:
Add multicast TTL and loopback properties.
Use the helper methods to implement ip4 and ip6.
* gst/udp/gstudpsrc.c: (gst_udpsrc_create), (gst_udpsrc_start):
* gst/udp/gstudpsrc.h:
Use the helper methods to implement ip4 and ip6.
Fixes #515962.