Codechange: Base CargoArray off std::array.

This avoids needing to define array accessors and allows use of
default value initialization.

src/misc_gui.cpp

@@ -167,7 +167,7 @@ public:
 
 		td.grf = nullptr;
 
-		CargoArray acceptance;
+		CargoArray acceptance{};
 		AddAcceptedCargo(tile, acceptance, nullptr);
 		GetTileDesc(tile, &td);