Add --warnings-fatal/-w option

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/fio.h b/fio.h
index 05aec80..d2cca11 100644
--- a/fio.h
+++ b/fio.h
@@ -522,6 +522,7 @@
 extern int fio_gtod_offload;
 extern int fio_gtod_cpu;
 extern enum fio_cs fio_clock_source;
+extern int warnings_fatal;
 
 extern struct thread_data *threads;