declaration of action::register php7 compatible

action.php

@@ -14,7 +14,7 @@ class action_plugin_dwcommits extends DokuWiki_Action_Plugin {
     /**
      * Register its handlers with the DokuWiki's event controller
      */
-    function register(&$controller) {
+    function register(Doku_Event_Handler $controller) {
         $controller->register_hook('PARSER_CACHE_USE', 'BEFORE', $this,
                                    'touch_cache');
     }