robots.txt recommendation wrong when language negotiation is domain based

On multilingual sites with language negotiation set to domain, url() always returns absolute URLs. So when your site runs on both http://example.com/ and http://example.nl/, url('flag') returns either http://example.com/flag or http://example.nl/flag. This causes the robots.txt recommendation to be wrong. It should suggest adding Disallow: /flag/, but now it recommends Disallow: http://example.com/flag/.

The following code replacement in flag.install fixes this:

Replace:

$flag_path = url('flag') . '/';

With:

$flag_path = url('flag') . '/';
// url() may return an absolute URL when language negotiation is set to domain
$flag_path = parse_url($flag_path, PHP_URL_PATH);