* include/std/functional (_Mu<_Arg, false, false>::operator()): Restore
	accidentally-removed volatile qualifier.
From-SVN: r231660
 2015-12-15  Jonathan Wakely  <jwakely@redhat.com>
 
+       * include/std/functional (_Mu<_Arg, false, false>::operator()): Restore
+       accidentally-removed volatile qualifier.
+
        * include/std/functional (is_placeholder, is_bind_expression): Update
        comments.
        (_Safe_tuple_element): Replace with _Safe_tuple_element_t alias
 
     public:
       template<typename _CVArg, typename _Tuple>
        _CVArg&&
-       operator()(_CVArg&& __arg, _Tuple&) const
+       operator()(_CVArg&& __arg, _Tuple&) const volatile
        { return std::forward<_CVArg>(__arg); }
     };