Codechange: Use ChunkHandlers sub-classes

src/order_base.h

@@ -32,7 +32,7 @@ extern OrderListPool _orderlist_pool;
  */
 struct Order : OrderPool::PoolItem<&_order_pool> {
 private:
-	friend void Load_VEHS();                                             ///< Loading of ancient vehicles.
+	friend struct VEHSChunkHandler;                             ///< Loading of ancient vehicles.
 	friend SaveLoadTable GetOrderDescription();                 ///< Saving and loading of orders.
 	/* So we can use private/protected variables in the saveload code */
 	friend class SlVehicleCommon;