Add missing copyright/license to a couple of files

include/boost/unordered/detail/implementation.hpp

@@ -1,6 +1,9 @@
 
 // Copyright (C) 2003-2004 Jeremy B. Maitin-Shepard.
 // Copyright (C) 2005-2016 Daniel James
+//
+// 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_UNORDERED_DETAIL_IMPLEMENTATION_HPP
 #define BOOST_UNORDERED_DETAIL_IMPLEMENTATION_HPP