Add blockalign/ba option

Allows the job to specify alignment of the IO specifically, instead
of relying on using blocksize as the offset alignment.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index b6ffe60..a9e2e3b 100644
--- a/fio.h
+++ b/fio.h
@@ -429,6 +429,7 @@
 	unsigned long long start_offset;
 
 	unsigned int bs[2];
+	unsigned int ba[2];
 	unsigned int min_bs[2];
 	unsigned int max_bs[2];
 	struct bssplit *bssplit;