Add ability for admin to cancel account_reminder emails for particular users

Issue Summary

Could you add the ability for the site administer to cancel the sending of account reminder emails for particular users? I get emailed requests from people who want to opt out but can't do so. I think some email problems truncate the opt-out link.

I found the line in the code which runs "UPDATE {account_reminder} SET msg_cnt = -1 WHERE uid = %d", $uid, so I am able to stop account_reminder for these people manually. But I'd like to be able to do it in the admin interface - possibly, by typing the uid into a field & then clicking Submit.

It would be even better if there could be an "deactivate account reminder" setting added to the "Update options" dropdown on admin/user/user, so that I could do it in bulk. This could be combined, maybe, with an "inactive" status on that page, so that I could see all the users who were currently receiving account reminders.