Provide ws2tcpip.h which is used instead of winsock2.h nowadays

[mstorsjo]

This fixes "make dummy".

[DimitriPapadopoulos]

Why is ws2tcpip.h use instead of winsock2.h?

According to the latest Programming reference for the Win32 API, all the functions used here are defined in the winsock2.h header.

MinGW also defines these functions in the winsock2.h header:
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-headers/include/winsock2.h

Of course I do understand that ws2tcpip.h includes ẁinsock2.h and defines additional functions resulting in a more modern API, but the minimal header required here is winsock2.h:
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-headers/include/ws2tcpip.h#l17

#include <winsock2.h>

Ah, got it! This code defines a socklen_t variable. which is then passed to getsockname(). But then the signature of getsockname() is:

int WSAAPI getsockname(
  [in]      SOCKET   s,
  [out]     sockaddr *name,
  [in, out] int      *namelen
);

I looks like int is sufficient. Do we really need socklen_t here?

[DimitriPapadopoulos]

I don't think we need socklen_t, see #5.