Codechange: Use const instead of magic number for ship order distance. Allow slightly further distance when following orders.

src/ship.h

@@ -48,6 +48,8 @@ struct Ship FINAL : public SpecializedVehicle<Ship, VEH_SHIP> {
 	void UpdateCache();
 };
 
+static const uint SHIP_MAX_ORDER_DISTANCE = 130;
+
 /**
  * Iterate over all ships.
  * @param var The variable used for iteration.