Update README to reflect that fio now runs on OpenBSD

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/README b/README
index 0acb04f..e90f493 100644
--- a/README
+++ b/README
@@ -297,10 +297,10 @@
 Platforms
 ---------
 
-Fio works on (at least) Linux, Solaris, AIX, HP-UX, OSX, NetBSD, Windows
-and FreeBSD.  Some features and/or options may only be available on some of
-the platforms, typically because those features only apply to that platform
-(like the solarisaio engine, or the splice engine on Linux).
+Fio works on (at least) Linux, Solaris, AIX, HP-UX, OSX, NetBSD, OpenBSD,
+Windows and FreeBSD.  Some features and/or options may only be available on
+some of the platforms, typically because those features only apply to that
+platform (like the solarisaio engine, or the splice engine on Linux).
 
 Some features are not available on FreeBSD/Solaris even if they could be
 implemented, I'd be happy to take patches for that. An example of that is