Fix regression with confirmation e-mails sent via Special:Confirmemail.

Fix regression with confirmation e-mails sent via Special:Confirmemail.
Recent changes to User object made User::sendConfirmationEmail() *not* save the new confirmation token to the database, which seems rather odd. As a result, you got a mail with a bogus value.

Since the function has side-effects, it pretty clearly needs to be saving its changes. Went ahead and had it do that rather than forcing all callers to fix its internal failing.