Move dsn property from the PDO to CI_DB_driver so other DB drivers can use it without declaring it
diff --git a/system/database/drivers/pdo/pdo_driver.php b/system/database/drivers/pdo/pdo_driver.php
index eadb78f..c8732ac 100644
--- a/system/database/drivers/pdo/pdo_driver.php
+++ b/system/database/drivers/pdo/pdo_driver.php
@@ -59,8 +59,7 @@
 	var $_count_string = "SELECT COUNT(*) AS ";
 	var $_random_keyword;
 
-	// need to track the pdo DSN, driver and options
-	var $dsn;
+	// need to track the pdo driver and options
 	var $pdodriver;
 	var $options = array();