DN should be escaped in DirectoryService::getMemberOf

[nixahnung]

Problem: If an DN had some escaped special Characters in the value (at my scenario it is a comma), then getMemberOf Method crashed with "wrong Credentials".

Added this Method (copied from moodle-code).
/** * Quote control characters in texts used in LDAP filters - see RFC 4515/2254 * * @param string filter string to quote * @return string the filter string quoted */ protected function ldap_filter_addslashes($text) { $text = str_replace('\\', '\\5c', $text); $text = str_replace(array('*', '(', ')', "\0"), array('\\2a', '\\28', '\\29', '\\00'), $text); return $text; }