focus_follow_movement caused flickering, fixed.

When using focus_follow_movement, client_focus() should be called only
if the target client is unfocused. Calling client_focus() on every motion
event causes an ugly flickering of the window.

Signed-off-by: Raphael Khaiat <raphael@khaiat.org>

src/event.c

@@ -637,6 +637,7 @@ motionnotify(XMotionEvent *ev)
           return;
 
      if((c = client_gb_win(ev->subwindow)))
+          if (c != sel)
                client_focus(c);
      
      return;