Implement the util_ldap_cache_getuserdn() API so that the ldap authorization...

Implement the util_ldap_cache_getuserdn() API so that the ldap authorization only modules have access to the util_ldap user cache without have to require ldap authentication as well.  Also required by mod_authnz_ldap so that it's authorization functionality can be used independant from the authentication functionality. [PR 31898]

Submitted by: Jari Ahonen [jah progress.com]
Reviewed by: Brad Nicholes


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@105667 13f79535-47bb-0310-9956-ffa450edef68