translate interval strings; translate more NickServ messages

* Translate interval strings to the user's language.

* Translate cookie emails and auth failure messages based on the
account's preferred language, rather than the user's preferred
language (they will not be authed, so they would get lang_C).
git-archimport-id: srvx@srvx.net--2004-srvx/srvx--devo--1.3--patch-39