Fix and improve BAR_WINTITLEACTIONS_PATCH (#442)

Introduced an unhideall function that can be used to reveal all hidden client in the current view.

Added a change to unmanage to avoid changing the window state from IconicState to WithdrawnState when the window manager stops managing windows (which happens when restarting).

Previously a hidden window would disappear when restarting dwm because:
   - when hidden the window would be unmapped and having the window state of IconicState
   - when restarting the window would remain unmapped while the window state would become WithdrawnState
   - which would prevent the window from being picked up by the scan function when the window manager starts

patch/bar_wintitleactions.c

@@ -92,3 +92,15 @@ showhideclient(const Arg *arg)
 	}
 }
 
+void
+unhideall(const Arg *arg)
+{
+	Client *c = NULL;
+	for (c = selmon->clients; c; c = c->next) {
+		if (ISVISIBLE(c)) {
+			XMapWindow(dpy, c->win);
+			setclientstate(c, NormalState);
+		}
+	}
+	arrange(selmon);
+}