Consider adding a way to retrieve parameter list without the class type

[ldionne]

Opened to track comment in https://lists.boost.org/Archives/boost/2017/04/234374.php:

I've a feeling that it might also be useful to provide an extractor that, for member pointers, returns just the arguments without the class.

Right now, args_t<void(foo::*)(float, char)> is std::tuple<foo&, float, char>. It might be useful to provide a way of retrieving the argument list without the type of *this, such that one would get std::tuple<float, char>.

[PrakashChoure2002]

hii This is my first time contributing this project . can you guide me and should i take this project.