Added changelog item, updated since version file headers
diff --git a/system/database/drivers/pdo/pdo_result.php b/system/database/drivers/pdo/pdo_result.php
index 5e136f5..e3ae0da 100644
--- a/system/database/drivers/pdo/pdo_result.php
+++ b/system/database/drivers/pdo/pdo_result.php
@@ -9,7 +9,7 @@
  * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.
  * @license		http://codeigniter.com/user_guide/license.html
  * @link		http://codeigniter.com
- * @since		Version 1.0
+ * @since		Version 2.1.0
  * @filesource
  */