Add options for disabling slat/clat/bw measurements

Useful for cutting down on the number of gettimeofday calls in
situations where that does impact performance. This is mostly for
really high IOPS rates.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.h b/fio.h
index 1484749..690afad 100644
--- a/fio.h
+++ b/fio.h
@@ -496,6 +496,9 @@
 	unsigned int zero_buffers;
 	unsigned int refill_buffers;
 	unsigned int time_based;
+	unsigned int disable_clat;
+	unsigned int disable_slat;
+	unsigned int disable_bw;
 
 	char *read_iolog_file;
 	char *write_iolog_file;