Return false to stop further processing of the tag
$reader: XMLReader object
+'ImportHandleUnknownUser': When a user does exist locally, this hook is called
+to give extensions an opportunity to auto-create it. If the auto-creation is
+successful, return false.
+$name: User name
+
'ImportHandleUploadXMLTag': When parsing a XML tag in a file upload.
Return false to stop further processing of the tag
$reader: XMLReader object