fluff: Make rollback of IPv6 addresses work properly

MediaWiki has two conventions for IPv6 addresses: sanitized and
prettified. The prettified form is only used when generating a user
link, i.e. "User (talk | contribs | block)"; everywhere else, you get
the sanitized form. This meant that the textual comparison of IPv6
addresses wasn't working, and multiple edits by the same IP address were
not all rolled back.
See also MediaWiki bug 44161.
Fixes #145.