socklen_t data type

[Eli Zaretskii]

Gnulib's sys/socket.h has this:

  # if @HAVE_WINSOCK2_H@
  /* Include headers needed by the emulation code.  */
  #  include <sys/types.h>
  #  include <io.h>

  #  if !GNULIB_defined_socklen_t
  typedef int socklen_t;
  #   define GNULIB_defined_socklen_t 1
  #  endif

  # endif

This unconditionally defines socklen_t on MS-Windows systems as a
signed int data type.  Why is this unconditional?  This page:

  https://pubs.opengroup.org/onlinepubs/007908799/xns/syssocket.h.html

says:

  <sys/socket.h> makes available a type, socklen_t, which is an
  unsigned opaque integral type of length of at least 32 bits.

So socklen_t could be an unsigned data type, which would then conflict
with the above.

And in fact mingw.org's MinGW recently changed the socklen_t data type
to be unsigned int, which breaks compilation of Gnulib's
sys_socket.c.  Is MinGW in error here?