[Bug c++/114620] Pointer-to-member template argument which is the member of a base class is rejected

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114620

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This also should be valid for C++17 +:
```
template<class M, char M::*> struct T{};
struct A{char x;};
struct B:A{  };
struct C:A{ T<B,(char B::*)&B::x> y; };
```

Note the constexpr case is only valid for C++17 + too.