Use id instead of full type for structs and unions
Use id instead of full type for structs and unions

    Structs and unions are always going to be private: they can only be
    exported by name. So we should just use their id for the sake of not
    having ridiculously long type names.

8l/myrddin,8l/myrddin,oridb/mc,oridb/mc,oridb/mc,oridb/mc