Make use of the accept4() API on OpenBSD.

From Brad, ok jca@

net/haproxy/Makefile

@@ -1,8 +1,9 @@
-# $OpenBSD: Makefile,v 1.34 2016/08/31 17:50:39 danj Exp $
+# $OpenBSD: Makefile,v 1.35 2016/09/27 17:04:58 danj Exp $
 
 COMMENT =	reliable, high performance TCP/HTTP load balancer
 
 DISTNAME =	haproxy-1.6.9
+REVISION =	0
 CATEGORIES =	net www
 HOMEPAGE =	http://www.haproxy.org/
 MAINTAINER =	Daniel Jakots <obsd@chown.me>

net/haproxy/patches/patch-Makefile

@@ -0,0 +1,19 @@
+$OpenBSD: patch-Makefile,v 1.3 2016/09/27 17:04:58 danj Exp $
+
+Make use of accept4() on OpenBSD.
+
+--- Makefile.orig	Sun Sep 25 23:13:40 2016
++++ Makefile	Sun Sep 25 23:14:35 2016
+@@ -304,10 +304,11 @@ ifeq ($(TARGET),osx)
+   USE_LIBCRYPT   = implicit
+ else
+ ifeq ($(TARGET),openbsd)
+-  # This is for OpenBSD >= 3.0
++  # This is for OpenBSD >= 5.7
+   USE_POLL       = implicit
+   USE_KQUEUE     = implicit
+   USE_TPROXY     = implicit
++  USE_ACCEPT4    = implicit
+ else
+ ifeq ($(TARGET),netbsd)
+   # This is for NetBSD