On Windows, ldap_delete_(ext_)s returns LDAP_UNWILLING_TO_PERFORM when trying to delete an entry that cannot be deleted. On Unix, LDAP_SERVER_DOWN is returned instead. Unix also returns LDAP_SERVER_DOWN immediately from ldap_delete_ext if the entry cannot be deleted, whereas Windows queues an asynchronous operation and returns LDAP_SUCCESS.
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54702
-- v2: wldap32: Handle null DN or null message in ldap_delete* and add tests.