gst/udp/gstudpsrc.*: Added "buffer" property to control the kernel receive buffer...

gst/udp/gstudpsrc.*: Added "buffer" property to control the kernel receive buffer size.

Original commit message from CVS:
Patch by: Thijs Vermeir <thijs dot vermeir at barco dot com>
* gst/udp/gstudpsrc.c: (gst_udpsrc_class_init), (gst_udpsrc_init),
(gst_udpsrc_create), (gst_udpsrc_set_property),
(gst_udpsrc_get_property), (gst_udpsrc_start):
* gst/udp/gstudpsrc.h:
Added "buffer" property to control the kernel receive buffer size.
Update documentation.
Small cleanups. Fixes #348752.
API: buffer property