XQuartz: if 0 out a block to avoid thread-unsafe lockups

(cherry picked from commit 60d7359a67900ad4601dbc73e07bcd8c803100a5)

hw/xquartz/X11Application.m

@@ -967,6 +967,7 @@ static void send_nsevent(NSEvent *e) {
                 pDev = darwinTabletCurrent;
             }
 
+#if 0 // XPlugin isn't thread safe ... sigh
             if(!quartzServerVisible) {
                 xp_window_id wid;
                 
@@ -982,6 +983,7 @@ static void send_nsevent(NSEvent *e) {
                 if (wid == 0)
                     return;        
             }
+#endif
             
             DarwinSendPointerEvents(pDev, ev_type, ev_button, pointer_x, pointer_y,
                                     pressure, tilt_x, tilt_y);