Rename pdodriver property to subdriver and make it available to all drivers
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index a994441..d326282 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -46,6 +46,7 @@
 	public $hostname;
 	public $database;
 	public $dbdriver		= 'mysql';
+	public $subdriver;
 	public $dbprefix		= '';
 	public $char_set		= 'utf8';
 	public $dbcollat		= 'utf8_general_ci';