[master] 3ed75f5 OpenBSD is not defined (unless sys/param.h is included) so simply use the gcc builtin define for it.

[Poul-Henning Kamp]

commit 3ed75f50638a9461f443337d61c0b4c9dcd3f766
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Sat Mar 9 08:39:21 2013 +0000

    OpenBSD is not defined (unless sys/param.h is included) so simply use the gcc
    builtin define for it.
    
    From:	"Federico G. Schwindt" <fgsch at lodoss.net>

diff --git a/bin/varnishd/mgt/mgt_shmem.c b/bin/varnishd/mgt/mgt_shmem.c
index 7707309..2e92df6 100644
--- a/bin/varnishd/mgt/mgt_shmem.c
+++ b/bin/varnishd/mgt/mgt_shmem.c
@@ -247,7 +247,7 @@ mgt_SHM_Create(void)
 		exit (-1);
 	}
 
-#ifdef OpenBSD
+#ifdef __OpenBSD__
 	/* Commit changes, for OS's without coherent VM/buf */
 	AZ(msync(p, getpagesize(), MS_SYNC));
 #endif