Change: Add CargoTypes type for cargo masks. (#6790)

src/cargotype.cpp

@@ -28,12 +28,12 @@ CargoSpec CargoSpec::array[NUM_CARGO];
  * Bitmask of cargo types available. This includes phony cargoes like regearing cargoes.
  * Initialized during a call to #SetupCargoForClimate.
  */
-uint32 _cargo_mask;
+CargoTypes _cargo_mask;
 
 /**
  * Bitmask of real cargo types available. Phony cargoes like regearing cargoes are excluded.
  */
-uint32 _standard_cargo_mask;
+CargoTypes _standard_cargo_mask;
 
 /**
  * Set up the default cargo types for the given landscape type.