Add seed values support for Query Builder order_by

(feature request #1987)
diff --git a/system/database/drivers/cubrid/cubrid_driver.php b/system/database/drivers/cubrid/cubrid_driver.php
index c89a924..8394139 100644
--- a/system/database/drivers/cubrid/cubrid_driver.php
+++ b/system/database/drivers/cubrid/cubrid_driver.php
@@ -64,6 +64,13 @@
 	 */
 	protected $_escape_char = '`';
 
+	/**
+	 * ORDER BY random keyword
+	 *
+	 * @var	array
+	 */
+	protected $_random_keyword = array('RANDOM()', 'RANDOM(%d)');
+
 	// --------------------------------------------------------------------
 
 	/**