include local configuration file once

When config.php was copied to config.inc.php it would result in a infinite
include loop.

conf/config.php

@@ -43,6 +43,6 @@ $CONFIG['socket'] = NULL;
 
 # load local configuration
 if (file_exists(dirname(__FILE__).'/config.local.php'))
-	include 'config.local.php';
+	include_once 'config.local.php';
 
 ?>