windows 10 supports unix domain sockets - add an option to use it instead of named-pipes for ipc://

[alzix]

we are experiencing issues with IPC sockets reliability on Windows. related issues #1175 and #1567
on macOS it works much more reliably. One of the differences between the two systems is that Windows uses named named-pipes for IPC, while UNIX domain sockets are used on macOS

Windows 10 supports UNIX domain sockets out of the box - https://devblogs.microsoft.com/commandline/af_unix-comes-to-windows/
Add a compile/runtime option to use UNIX domain sockets on Windows for IPC

[gdamore]

I'm going to hold on this for now -- but I think I might well do this. I'd like to update both legacy nanomsg and mangos to do this as well, because it is an interoperability problem.

One other idea is to add a new URL scheme and transport just for UNIX sockets. I am thinking about that too.

[gdamore]

This will be post 1.6.0. But I do intend to do it.

[gdamore]

So my plan of record is as follows:

1. Add unix:// as a UNIX domain IPC URL. Will be available unconditionally when supported.
2. Add winpipe:// as a new scheme that only supports Windows named pipes. Available on Windows and compatible with legacy IPC.
3. Add a compile time option to select whether ipc:// is unix:// or winpipe:// - will default to winpipe:// for 1.x, but I think in NNG 2.0 will change the default to IPC because honestly named pipes are a pain in my arse and I want to kick them to the curb.

Mangos will probably grow the same scheme as well.