Fix zlib symbol conflicts

fix #808

test/beast/zlib/zlib.cpp

@@ -0,0 +1,12 @@
+//
+// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/beast
+//
+
+// Make sure symbols don't confict with ZLib
+#include "zlib-1.2.11/zlib.h"
+#include <boost/beast/zlib.hpp>