x11: fix enter/leave events for frames

We need to pass all events on frames to GTK, even if we handled
them internally, to make sure that the hover state is properly
updated.

src/core/events.c

@@ -952,6 +952,10 @@ handle_input_xevent (MetaDisplay *display,
       break;
     }
 
+  /* Don't eat events for GTK frames (we need to update the :hover state on buttons) */
+  if (window && window->frame && modified == window->frame->xwindow)
+    return FALSE;
+
   /* Don't pass these events through to Clutter / GTK+ */
   return TRUE;
 }