docs: Enable and fix gtk-doc warnings

* Makefile: Enable gtk-doc warnings, like the rest of GStreamer
 * addresspool/mediafactory: Add missing annotation colon
 * stream: Annotate return value

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=725528

gst/rtsp-server/Makefile.am

@@ -75,6 +75,7 @@ GstRtspServer-@GST_API_VERSION@.gir: $(INTROSPECTION_SCANNER) libgstrtspserver-@
 		$(INTROSPECTION_SCANNER) -v --namespace GstRtspServer \
 		--nsversion=@GST_API_VERSION@ \
 		--strip-prefix=Gst \
+		--warn-all \
 		-I$(top_srcdir) \
 		-I$(top_builddir) \
 		-DIN_GOBJECT_INTROSPECTION=1 \

gst/rtsp-server/rtsp-address-pool.c

@@ -625,7 +625,7 @@ find_address_in_ranges (GList * addresses, Addr * addr, guint port,
  * @port: The first port to reserve
  * @n_ports: The number of ports
  * @ttl: The requested ttl
- * @address: (out) storage for a #GstRTSPAddress
+ * @address: (out): storage for a #GstRTSPAddress
  *
  * Take a specific address and ports from @pool. @n_ports consecutive
  * ports will be allocated of which the first one can be found in

gst/rtsp-server/rtsp-media-factory.c

@@ -1053,7 +1053,7 @@ default_configure (GstRTSPMediaFactory * factory, GstRTSPMedia * media)
  * implementation of this function returns the bin created from the
  * launch parameter.
  *
- * Returns: (transfer floating) a new #GstElement.
+ * Returns: (transfer floating): a new #GstElement.
  */
 GstElement *
 gst_rtsp_media_factory_create_element (GstRTSPMediaFactory * factory,

gst/rtsp-server/rtsp-stream.c

@@ -2186,8 +2186,8 @@ gst_rtsp_stream_remove_transport (GstRTSPStream * stream,
  *
  * @stream must be joined to a bin.
  *
- * Returns: the RTP socket or %NULL if no socket could be allocated for @family.
- *     Unref after usage
+ * Returns: (transfer full): the RTP socket or %NULL if no socket could be
+ *     allocated for @family. Unref after usage
  */
 GSocket *
 gst_rtsp_stream_get_rtp_socket (GstRTSPStream * stream, GSocketFamily family)
@@ -2220,8 +2220,8 @@ gst_rtsp_stream_get_rtp_socket (GstRTSPStream * stream, GSocketFamily family)
  *
  * @stream must be joined to a bin.
  *
- * Returns: the RTCP socket or %NULL if no socket could be allocated for
- *     @family. Unref after usage
+ * Returns: (transfer full): the RTCP socket or %NULL if no socket could be
+ *     allocated for @family. Unref after usage
  */
 GSocket *
 gst_rtsp_stream_get_rtcp_socket (GstRTSPStream * stream, GSocketFamily family)