9.36: added incoming TS6 command TMODE handler.
            user ->change_nick() method now takes an optional $time parameter for the nick TS.
            the $over_protocol argument for channel methods ->handle_mode_string(), ->do_mode_string(), and friends can now optionally be a subroutine to look up a user by UID.
            fixed some various bugs with user away messages due to improper use of exists() instead of length().