[PATCH] [libc++] Fix PR20084 - std::is_function<void() const> failed.

[Marshall Clow]

Look at `__member_pointer_traits_imp` for a crappy way to do it.

Also, I'm not sure if  `std::function<void (int, ...) const>`, is even legal, but if it is, that's more work.


http://reviews.llvm.org/D7573

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/