mod_authnz_ldap: Add an AuthLDAPRemoteUserAttribute directive. If

set, REMOTE_USER will be set to this attribute, rather than the
username supplied by the user. Useful for example when you want users
to log in using an email address, but need to supply a userid instead
to the backend.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@463427 13f79535-47bb-0310-9956-ffa450edef68