Add a 'continue_on_error' option to fio

Add option to make fio continue on non-fatal errors.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/ioengine.h b/ioengine.h
index 9c0ed9a..6190977 100644
--- a/ioengine.h
+++ b/ioengine.h
@@ -139,6 +139,7 @@
 extern struct io_u *__get_io_u(struct thread_data *);
 extern struct io_u *get_io_u(struct thread_data *);
 extern void put_io_u(struct thread_data *, struct io_u *);
+extern void clear_io_u(struct thread_data *, struct io_u *);
 extern void requeue_io_u(struct thread_data *, struct io_u **);
 extern int __must_check io_u_sync_complete(struct thread_data *, struct io_u *, unsigned long *);
 extern int __must_check io_u_queued_complete(struct thread_data *, int, unsigned long *);