Pointer to member support

[TartanLlama]

Pointer to members are not supported, so given a type s:

struct s {
  int get_42() { return 42; }
};
std::vector<s> input (10);
std::vector<int> results;

I have to write:

  input >>= pipes::funnel
    >>= pipes::transform([](auto&& x) { return x.get_42(); })
    >>= back_inserter(results);

instead of:

  input >>= pipes::funnel
    >>= pipes::transform(&s::get_42})
    >>= back_inserter(results);

[joboccara]

Indeed, thanks. This should be fixed with this commit.