patch to silence clang warning

[SVN r74441]

include/boost/fusion/algorithm/iteration/detail/fold.hpp

@@ -186,7 +186,7 @@ namespace boost { namespace fusion
         {
             template<typename State, typename It0, typename F>
             static Result
-            call(State const& state,It0 const& it0,F f)
+            call(State const& state,It0 const& it0, F)
             {
                 return static_cast<Result>(state);
             }