add boost on mac

macx64/include/boost/chrono/clock_string.hpp

@@ -0,0 +1,25 @@
+//
+//  (C) Copyright 2010-2011 Vicente J. Botet Escriba
+//  Use, modification and distribution are subject to 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_CHRONO_CLOCK_STRING_HPP
+#define BOOST_CHRONO_CLOCK_STRING_HPP
+
+#include <string>
+
+namespace boost
+{
+  namespace chrono
+  {
+
+    template<class Clock, class CharT>
+    struct clock_string;
+
+  } // chrono
+
+} // boost
+
+#endif  // BOOST_CHRONO_CLOCK_STRING_HPP