[horde] authentication with different database

[Mike Cochrane]

> ----- Message from aaron at vafishfreek.com ---------
> 
> There has got to be a setting some place that tells horde what fields to
> cross reference within the database table.
Only in HEAD... from the comment in the top of horde/lib/Auth/sql.php

* Optional values:
*   'table'          The name of the SQL table to use in 'database'.
*                    Defaults to 'horde_users'.
*   'username_field' The name of the username field in the auth table.
*                    Defaults to 'user_uid'.
*   'password_field' The name of the password field in the auth table.
*                    Defaults to 'user_pass'.

- Mike :-)