clutter: Set slave=master in IM forwarded key events

The fix is twofold. On one hand, it makes sense not to relate IM (nor
any other) generated events to a HW device. On the other hand, if we
are unfortunate that an IM event is in flight when we are switching
to another TTY, it may arrive at a time when the source device is no
longer existent.

clutter/clutter/clutter-input-method.c

@@ -353,6 +353,7 @@ clutter_input_method_notify_key_event (ClutterInputMethod *im,
       copy = clutter_event_copy (event);
       clutter_event_set_flags (copy, clutter_event_get_flags (event) |
                                CLUTTER_EVENT_FLAG_INPUT_METHOD);
+      clutter_event_set_source_device (copy, clutter_event_get_device (copy));
       clutter_event_put (copy);
       clutter_event_free (copy);
     }