Bug 1713 - You can't check the existence of a typedef using the preprocessor. Added a preprocessor check. Also removed an overqualified method name.
// Copyright Daniel James 2005-2006. 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)
// Based on Peter Dimov's proposal
// http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1756.pdf
// issue 6.18.
#include <boost/functional/hash/hash.hpp>