blktrace replay: delay support

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 870b670..fa0edb1 100644
--- a/fio.h
+++ b/fio.h
@@ -522,6 +522,7 @@
 	struct timeval start;	/* start of this loop */
 	struct timeval epoch;	/* time job was started */
 	struct timeval rw_end[2];
+	struct timeval last_issue;
 	unsigned int rw_end_set[2];
 
 	/*