Add tests between each language

[d-perl]

There should be a test along the lines of

for language in supported_languages:
    for message_type in message_types:
        msg = create_message_in_language(message_type)
        for lang in other_langs:
            parsed = parse_message_in_lang(lang, msg)
            assert validates_against_schema(parsed)
            assert can_be_coerced_to_type(parsed)