Optional's Assignment fixed

[SVN r28412]

include/boost/none_t.hpp

@@ -0,0 +1,24 @@
+// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
+//
+// Use, modification, and distribution is 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//
+#ifndef BOOST_NONE_T_17SEP2003_HPP
+#define BOOST_NONE_T_17SEP2003_HPP
+
+namespace boost {
+
+namespace detail { struct none_helper{}; }
+
+typedef int detail::none_helper::*none_t ;
+
+} // namespace boost
+
+#endif
+