Add seed values support for Query Builder order_by

(feature request #1987)
diff --git a/system/database/drivers/sqlite3/sqlite3_driver.php b/system/database/drivers/sqlite3/sqlite3_driver.php
index 9a2c1ee..f0818ae 100644
--- a/system/database/drivers/sqlite3/sqlite3_driver.php
+++ b/system/database/drivers/sqlite3/sqlite3_driver.php
@@ -54,9 +54,9 @@
 	/**
 	 * ORDER BY random keyword
 	 *
-	 * @var	string
+	 * @var	array
 	 */
-	protected $_random_keyword = ' RANDOM()';
+	protected $_random_keyword = array('RANDOM()', 'RANDOM()');
 
 	// --------------------------------------------------------------------