Make sure we cycle through existing client's group membership and set

the hidden state on the group; important to know group hidden state
after a re-exec or restart of cwm (as easily seen in group menu).

screen.c

@@ -69,6 +69,7 @@ screen_init(int which)
 		XFree(wins);
 	}
 	screen_updatestackingorder(sc);
+	group_set_state(sc);
 
 	if (HasRandr)
 		XRRSelectInput(X_Dpy, sc->rootwin, RRScreenChangeNotifyMask);