fixed missing ns for xlink in WFS

SE/se-lib/Api/WfsDataServer.php

@@ -262,6 +262,7 @@ if($DBG){echo 'getItems:';print_r($searchParams);echo "\n";}
 		$rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:wfs', 'http://www.opengis.net/wfs');
 		$rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:gml', 'http://www.opengis.net/gml');
 		$rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:xsi', 'http://www.w3.org/2001/XMLSchema-instance');
+		$rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:xlink', 'http://www.w3.org/1999/xlink');
 		$rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:' . $wfsNs, $wfsNsUri);
 		if (!$simple) $rootNode->setAttributeNS('http://www.w3.org/2000/xmlns/', "xmlns:{$rootWfsNs}", $rootWfsNsUri);
 		//$rootNode->setAttribute('xsi:schemaLocation', 'http://www.opengis.net/wfs');