Docs update.

src/utils/Utils.js

@@ -96,6 +96,8 @@ Phaser.Utils = {
     /**
     * This is a slightly modified version of http://api.jquery.com/jQuery.extend/
     * @method Phaser.Utils.extend
+    * @param {boolean} deep - Perform a deep copy?
+    * @param {object} target - The target object to copy to.
     * @return {object} The extended object.
     */
 	extend: function () {