Codechange: migrate size related functions to Map structure

src/cheat_gui.cpp

@@ -133,7 +133,7 @@ static int32 ClickChangeMaxHlCheat(int32 p1, int32 p2)
 
 	/* Check if at least one mountain on the map is higher than the new value.
 	 * If yes, disallow the change. */
-	for (TileIndex t = 0; t < MapSize(); t++) {
+	for (TileIndex t = 0; t < Map::Size(); t++) {
 		if ((int32)TileHeight(t) > p1) {
 			ShowErrorMessage(STR_CONFIG_SETTING_TOO_HIGH_MOUNTAIN, INVALID_STRING_ID, WL_ERROR);
 			/* Return old, unchanged value */