Workaround for LWG 2408: SFINAE-friendly std::iterator_traits.

Now available for GCC(libstdc++v3) < 4.5 and MSVC 12.0.
It means, there is no ambiguous about calling next/prior/... via ADL.

include/boost/fusion/adapted/boost_tuple/boost_tuple_iterator.hpp

@@ -207,6 +207,15 @@ namespace boost { namespace fusion
     };
 }}
 
+#ifdef BOOST_FUSION_WORKAROUND_FOR_LWG_2408
+namespace std
+{
+    template <typename Cons>
+    struct iterator_traits< ::boost::fusion::boost_tuple_iterator<Cons> >
+    { };
+}
+#endif
+
 #endif