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/DB_driver.php b/system/database/DB_driver.php
index af496aa..025441f 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -40,6 +40,7 @@
  */
 class CI_DB_driver {
 
+	public $dsn;
 	public $username;
 	public $password;
 	public $hostname;