userdatdupe() to match the passed login-id (username):
*  This allows more permissive username matching, e.g. if your user name
   is "Analog Kid", you could login with "analogkid", "analog.kid" or
   "analog_kid", which is handy when passing a user name on the command
   line (e.g. to an ssh client) for example.
*  This is the same function used for Telnet logins via exec/login.js