Send a 401 Unauthorized header in XML-RPC when access is denied

This is far from perfect but should solve most issues in the recommended
configuration where only authorized users have access. Sending proper
status codes should be implemented when the API implementation
refactoring is done.

lib/exe/xmlrpc.php

@@ -53,6 +53,7 @@ function addCallback($method, $callback, $args, $help, $public=false){
      */
     function call($methodname, $args){
         if(!in_array($methodname,$this->public_methods) && !$this->checkAuth()){
+            header('HTTP/1.1 401 Unauthorized');
             return new IXR_Error(-32603, 'server error. not authorized to call method "'.$methodname.'".');
         }
         return parent::call($methodname, $args);