New offset_increment option

This patch adds a new option to fio job files. It is described
in the HOWTO as follows:

offset_increment=int	If this is provided, then the real offset becomes
		the offset + offset_increment * thread_number, where the
		thread number is a counter that starts at 0 and is incremented
		for each job. This option is useful if there are several jobs
		which are intended to operate on a file in parallel in disjoint
		segments, with even spacing between the starting points.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/ioengines.c b/ioengines.c
index 4c609f2..1a0898d 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -278,6 +278,7 @@
 	 */
 	if (io_u->error == EINVAL && td->io_issues[io_u->ddir & 1] == 1 &&
 	    td->o.odirect) {
+
 		log_info("fio: first direct IO errored. File system may not "
 			 "support direct IO, or iomem_align= is bad.\n");
 	}