Support unix domain sockets under Win10

[casabre]

Issue description

Hi there,
thanks for the great work but I have a feature request regarding unix domain sockets on Windows 10. According to the following blog article, Win10 supports now AF_UNIX domain sockets. If I use ipc://, a not supported socket type will be reported. Thus, could please extend the compatible Win10 sockets to AF_UNIX as well. The support of the utilized Win10 version can be checked by sc query afunix

Please see also #1327@pyzmq

Environment

• libzmq version (commit hash if unreleased): 18.1
• OS: Windows 10

Minimal test code / Steps to reproduce the issue

use pyzmq

import zmq
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind('ipc:///tmp/stream')

What's the actual result? (include assertion message & call stack if applicable)

Traceback (most recent call last):
File "", line 1, in
File "zmq\backend\cython\socket.pyx", line 550, in zmq.backend.cython.socket.Socket.bind
File "zmq\backend\cython\checkrc.pxd", line 25, in zmq.backend.cython.checkrc._check_rc
zmq.error.ZMQError: Protocol not supported

What's the expected result?

Bound or connected socket

[bluca]

This was discussed in #3507 and #3104 and #1808

Pull requests to implement support for this are welcome

[sigiesec]

Indeed, Win10 supports AF_UNIX now. This will require some adaptations in libzmq, since this is still done via the Windows flavour of the socket API.

For the ipc transport this will probably work.