Merge iostreams, hash.

Including disallowing implicit casts to `hash_value`.


[SVN r63812]

test/implicit_fail_test.cpp

@@ -0,0 +1,21 @@
+
+// Copyright 2010 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)
+
+#include <boost/functional/hash.hpp>
+
+namespace test
+{
+    struct base {};
+    std::size_t hash_value(base const&) { return 0; }
+    
+    struct converts { operator base() const { return base(); } };
+}
+
+int main() {
+    boost::hash<test::converts> hash;
+    test::converts x;
+    
+    hash(x);
+}