allow group authorization to be stored in either basic or digest dbm user

files. This is done by looking up first "$user:$realm" and if no success
then $user as key.
The patch also restores the possibility of group files only
($user -> group,group... or "$user:$realm" -> group,group...).
That got somehow lost during the auth rewrite.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@98175 13f79535-47bb-0310-9956-ffa450edef68