DocBlocks for base DB classes

Partially fixes issue #1295.
diff --git a/system/database/DB.php b/system/database/DB.php
index 676cb9c..79e5c7a 100644
--- a/system/database/DB.php
+++ b/system/database/DB.php
@@ -32,8 +32,10 @@
  * @category	Database
  * @author	EllisLab Dev Team
  * @link	http://codeigniter.com/user_guide/database/
- * @param 	string
- * @param 	bool	Determines if query builder should be used or not
+ *
+ * @param 	string|string[]	$params
+ * @param 	bool		$query_builder_override
+ *				Determines if query builder should be used or not
  */
 function &DB($params = '', $query_builder_override = NULL)
 {
@@ -149,11 +151,22 @@
 		require_once(BASEPATH.'database/DB_query_builder.php');
 		if ( ! class_exists('CI_DB'))
 		{
+			/**
+			 * CI_DB
+			 *
+			 * Acts as an alias for both CI_DB_driver and CI_DB_query_builder.
+			 *
+			 * @see	CI_DB_query_builder
+			 * @see	CI_DB_driver
+			 */
 			class CI_DB extends CI_DB_query_builder { }
 		}
 	}
 	elseif ( ! class_exists('CI_DB'))
 	{
+		/**
+	 	 * @ignore
+		 */
 		class CI_DB extends CI_DB_driver { }
 	}