Bugfix: Re-implement reconfiguring height of dock windows (+test) (Thanks thomasba)

include/data.h

@@ -230,16 +230,6 @@ struct xoutput {
     /** x, y, width, height */
     Rect rect;
 
-#if 0
-    /** The bar window */
-    xcb_window_t bar;
-    xcb_gcontext_t bargc;
-
-    /** Contains all clients with _NET_WM_WINDOW_TYPE ==
-     * _NET_WM_WINDOW_TYPE_DOCK */
-    SLIST_HEAD(dock_clients_head, Client) dock_clients;
-#endif
-
     TAILQ_ENTRY(xoutput) outputs;
 };