Add a forward header for the hash functions.

[SVN r32586]

include/boost/functional/hash_fwd.hpp

@@ -0,0 +1,41 @@
+
+//  (C) Copyright Daniel James 2005.
+//  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. 
+
+#if !defined(BOOST_FUNCTIONAL_HASH_FWD_HPP)
+#define BOOST_FUNCTIONAL_HASH_FWD_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+#include <boost/config.hpp>
+#include <cstddef>
+#include <boost/detail/workaround.hpp>
+
+namespace boost
+{
+    template <class T> struct hash;
+
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
+    template <class T> void hash_combine(std::size_t& seed, T& v);
+#else
+    template <class T> void hash_combine(std::size_t& seed, T const& v);
+#endif
+
+    template <class It> std::size_t hash_range(It, It);
+    template <class It> void hash_range(std::size_t&, It, It);
+
+#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
+    template <class T> inline std::size_t hash_range(T*, T*);
+    template <class T> inline void hash_range(std::size_t&, T*, T*);
+#endif
+}
+
+#endif