x11: Avoid spurious focus events on grabs

We want to avoid handling focus events for the private focus window,
otherwise the keyboard grab taken by for example buttons will cause a
spurious FOCUS_OUT/FOCUS_IN on the toplevel.

The code that did this seems to have been lost in the XI2 transition for
GTK3.

https://bugzilla.gnome.org/show_bug.cgi?id=657578

gdk/x11/gdkdevicemanager-xi2.c

@@ -1228,6 +1228,7 @@ gdk_x11_device_manager_xi2_translate_event (GdkEventTranslator *translator,
                                              GUINT_TO_POINTER (xev->sourceid));
 
         _gdk_device_manager_core_handle_focus (window,
+                                               xev->event,
                                                device,
                                                source_device,
                                                (ev->evtype == XI_FocusIn) ? TRUE : FALSE,