Match IPv6 addresses as anonymous users

[strainu]

This should solve https://bugzilla.wikimedia.org/show_bug.cgi?id=56560

[schmir]

thanks for your pull request.

doesn't the same argument as seen in #41 apply here? are IPv6 addresses valid usernames?

[strainu]

I don't think so. I've tried to create users 2001::a and 2001:a:b:c:d:e:1:2 and they were rejected as invalid. Perhaps a weird, cornercase address would work, but that would be a bug (IPv4 addresses definitely don't work ). Even if such a user would be able to register, it would still be against the policies on most WMF projects.

[schmir]

Thanks, I've merged that one.