Added a default _insert_batch() method instead of requiring each driver to define it and fixed 2 issues related to it
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index 0a96f3f..307524f 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -653,7 +653,7 @@
 
 		for ($i = 0, $c = count($values); $i < $c; $i++)
 		{
-			$sql .= '	INTO '.$table.' ('.$keys.') VALUES '.$values[$i].'\n';
+			$sql .= '	INTO '.$table.' ('.$keys.') VALUES '.$values[$i]."\n";
 		}
 
 		return $sql.'SELECT * FROM dual';