Improve submission latency calculation

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 12afa06..259166f 100644
--- a/fio.h
+++ b/fio.h
@@ -614,6 +614,7 @@
 extern void requeue_io_u(struct thread_data *, struct io_u **);
 extern long io_u_sync_complete(struct thread_data *, struct io_u *, endio_handler *);
 extern long io_u_queued_complete(struct thread_data *, int, endio_handler *);
+extern void io_u_queued(struct thread_data *, struct io_u *);
 
 /*
  * io engine entry points