$OpenBSD: patch-Makefile,v 1.5 2016/11/26 12:29:50 danj Exp $

Make use of accept4() on OpenBSD.

Committed upstream
http://git.haproxy.org/?p=haproxy.git;a=commit;h=9705ba2981016dd6b3b8d690bb8935a396cc0994

--- Makefile.orig	Sun Nov 20 22:42:20 2016
+++ Makefile	Sat Nov 26 13:07:05 2016
@@ -303,10 +303,11 @@ ifeq ($(TARGET),osx)
   USE_TPROXY     = implicit
 else
 ifeq ($(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
