fix userlist presence tracking; "version" command on all services
* Change scan_handle_presence() to scan_user_presence(), since we always
have the userData* at the caller site.
* Make handle_auth() respect user suspensions.
* In handle_part(), let scan_user_presence() update "seen" time.
* Make ChanServ adduser command take arguments in the "expected" order
("!adduser target level", not "!adduser level target")
* Add the "version" command to all built-in services
git-archimport-id: srvx@srvx.net--2004-srvx/srvx--devo--1.3--patch-7