Added thirdparty: boost library

thirdparty/include/boost/contract/detail/none.hpp

@@ -0,0 +1,28 @@
+
+#ifndef BOOST_CONTRACT_DETAIL_NONE_HPP_
+#define BOOST_CONTRACT_DETAIL_NONE_HPP_
+
+// Copyright (C) 2008-2018 Lorenzo Caminiti
+// Distributed under the Boost Software License, Version 1.0 (see accompanying
+// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
+// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
+
+namespace boost { namespace contract { namespace detail {
+
+// Tag for "no type".
+struct none {
+    // Some lib code use this to avoid unused local var warnings on #if, etc.
+    static none& value() {
+        static none none_value;
+        return none_value;
+    }
+};
+
+// Transform `void` to `none` type (for convenience, instead of using MPL).
+template<typename T> struct none_if_void { typedef T type; };
+template<> struct none_if_void<void> { typedef none type; };
+
+} } } // namespace
+
+#endif // #include guard
+