[libsigc++2/variadic_mem_fun2] mem_functor_base: Use member_method_result<>::type.

[Murray Cumming <murrayc src gnome org>]

commit 90373514defc9d7c5ced99f704feca835bc35803
Author: Murray Cumming <murrayc murrayc com>
Date:   Sun Mar 6 00:07:54 2016 +0100

    mem_functor_base: Use member_method_result<>::type.
    
    To avoid the (apparent) need to use T_args... with std::result_of_t<>.

 sigc++/functors/macros/mem_fun.h.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/sigc++/functors/macros/mem_fun.h.m4 b/sigc++/functors/macros/mem_fun.h.m4
index 89b9147..b555bf8 100644
--- a/sigc++/functors/macros/mem_fun.h.m4
+++ b/sigc++/functors/macros/mem_fun.h.m4
@@ -175,7 +175,7 @@ public:
   using object_type = typename member_method_class<T_func>::type;
 
   using function_type = T_func;
-  using result_type = std::result_of_t<T_func(object_type*, T_arg...)>;
+  using result_type = typename member_method_result<T_func>::type;
 
   using obj_type_with_modifier = typename std::conditional_t<
     member_method_is_const<T_func>::value, const object_type, object_type>;