Put the minimum amount of implementation in the same namespace as the 'using namespace' directives in order to avoid Visual C++ 8 bug.

[SVN r54024]

test/Jamfile.v2

@@ -38,6 +38,7 @@ test-suite functional/hash
         [ run link_ext_test.cpp link_no_ext_test.cpp ]
         [ run container_fwd_test.cpp ]
         [ compile-fail hash_no_ext_fail_test.cpp ]
+        [ compile-fail namespace_fail_test.cpp ]
         [ run hash_no_ext_macro_1.cpp ]
         [ run hash_no_ext_macro_2.cpp ]
     ;

test/namespace_fail_test.cpp

@@ -0,0 +1,6 @@
+#include <list>
+#include <boost/functional/hash/detail/float_functions.hpp>
+
+typedef list<int> foo;
+
+int main() {}