docs: fix up interfaces library docs to make gtk-doc happy

gst-libs/gst/interfaces/navigation.c

@@ -752,6 +752,9 @@ gst_navigation_event_parse_key_event (GstEvent * event, const gchar ** key)
  * a mouse button release event. Determine which type the event is using
  * gst_navigation_event_get_type() to retrieve the #GstNavigationEventType.
  *
+ * Returns: TRUE if the button number and both coordinates could be extracted,
+ *     otherwise FALSE.
+ *
  * Since: 0.10.23
  */
 gboolean
@@ -788,6 +791,8 @@ gst_navigation_event_parse_mouse_button_event (GstEvent * event, gint * button,
  * Inspect a #GstNavigation mouse movement event and extract the coordinates
  * of the event.
  *
+ * Returns: TRUE if both coordinates could be extracted, otherwise FALSE.
+ *
  * Since: 0.10.23
  */
 gboolean
@@ -820,6 +825,8 @@ gst_navigation_event_parse_mouse_move_event (GstEvent * event, gdouble * x,
  * Inspect a #GstNavigation command event and retrieve the enum value of the
  * associated command.
  *
+ * Returns: TRUE if the navigation command could be extracted, otherwise FALSE.
+ *
  * Since: 0.10.23
  */
 gboolean

gst-libs/gst/interfaces/xoverlay.c

@@ -473,7 +473,7 @@ gst_x_overlay_handle_events (GstXOverlay * overlay, gboolean handle_events)
  * This method is needed for non fullscreen video overlay in UI toolkits that do
  * not support subwindows.
  *
- * Return: %FALSE if not supported by the sink.
+ * Returns: %FALSE if not supported by the sink.
  *
  * Since: 0.10.29
  */

gst-libs/gst/interfaces/xoverlay.h

@@ -56,6 +56,7 @@ typedef struct _GstXOverlayClass GstXOverlayClass;
  * @set_xwindow_id: virtual method to configure the XWindow id
  * @expose: virtual method to handle expose events
  * @handle_events: virtual method to handle events
+ * @set_render_rectangle: virtual method to set the render rectange (since 0.10.29)
  *
  * #GstXOverlay interface
  */