add boost on mac

macx64/include/boost/yap/config.hpp

@@ -0,0 +1,21 @@
+// Copyright (C) 2016-2018 T. Zachary Laine
+//
+// 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)
+#ifndef BOOST_YAP_CONFIG_HPP_INCLUDED
+#define BOOST_YAP_CONFIG_HPP_INCLUDED
+
+
+#ifndef BOOST_NO_CONSTEXPR_IF
+/** Indicates whether the compiler supports constexpr if.
+
+    If the user does not define any value for this, we assume that the
+    compiler does not have the necessary support.  Note that this is a
+    temporary hack; this should eventually be a Boost-wide macro. */
+#define BOOST_NO_CONSTEXPR_IF
+#elif BOOST_NO_CONSTEXPR_IF == 0
+#undef BOOST_NO_CONSTEXPR_IF
+#endif
+
+#endif