Fix PR 54463 by removing an optional 'standard' parameter.
It has been no-une for more than 10 years and is not documented.
This also makes the code more consistent with other mod_auth modules.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1484398 13f79535-47bb-0310-9956-ffa450edef68