Optimize menu sorting

Sorting and deduplicating elements after all items have been registered
improves the time complexity of constructing the item list from O(n^2)
to O(n log n). On a system with about 4000 menu items, this reduces
startup time from about 0.21 seconds to 0.13 seconds.

wmenu.c

@@ -13,7 +13,7 @@ static void read_items(struct menu *menu) {
 		if (p) {
 			*p = '\0';
 		}
-		menu_add_item(menu, strdup(buf), false);
+		menu_add_item(menu, strdup(buf));
 	}
 }