Added placeholder migration script

modules/Migration/schema/650_to_660.php

+<?php
+/*+********************************************************************************
+ * The contents of this file are subject to the vtiger CRM Public License Version 1.0
+ * ("License"); You may not use this file except in compliance with the License
+ * The Original Code is:  vtiger CRM Open Source
+ * The Initial Developer of the Original Code is vtiger.
+ * Portions created by vtiger are Copyright (C) vtiger.
+ * All Rights Reserved.
+ *********************************************************************************/
+
+if(defined('VTIGER_UPGRADE')) {
+global $adb;
+
+}
+