* glib/dbus-gproxy.c (struct DBusGProxy): convert to a GObject
	subclass. This means dropping the transparent thread safety of the
	proxy; you now need a separate proxy per-thread, or your own
	locking on the proxy. Probably right anyway.
	(dbus_gproxy_ref, dbus_gproxy_unref): nuke, just use g_object_ref