wayland: Add API for disabling the event dispatching

This allows the integration of Clutter with another library, like GTK+,
that is dispatching the events itself. This is implemented by calling
into the cogl_wayland_renderer_set_event_dispatch_enabled() and since
that function must be called on the newly created renderer the newly
added clutter_wayland_disable_event_retrieval must be called before
clutter_init()

https://bugzilla.gnome.org/show_bug.cgi?id=704279

doc/reference/clutter/clutter-sections.txt

@@ -1436,6 +1436,7 @@ clutter_wayland_input_device_get_wl_seat
 clutter_wayland_stage_get_wl_shell_surface
 clutter_wayland_stage_get_wl_surface
 clutter_wayland_set_display
+clutter_wayland_disable_event_retrieval
 </SECTION>
 
 <SECTION>