mod_auth_fast - add a way to invalidate a certain user token(s)

[licaon-kter]

Environment

• ejabberd version: ed846c4
• OS: Linux (Debian)
• Installed from: source

eg. I was expecting kick_user to kill their session and token, but it did not

the Admin panel Mnesia page offers only global "clear" for all users, and this can't be stored in SQL (which I hope would allow more granular control)