gst/: Patch from Alessandro Decina adding get_type_full and get_protocols_full private vfuncs to the URIHandler inter...

Original commit message from CVS:
* gst/gstelementfactory.c: (gst_element_register):
* gst/gsturi.h:
Patch from Alessandro Decina adding get_type_full and
get_protocols_full private vfuncs to the URIHandler interface
to allow bindings to support creating URI handlers.
Partially fixes: #339279
API: GstURIHandlerInterface::get_type_full
API: GstURIHandlerInterface::get_protocols_full