Allow creating sockets from raw file descriptors

[valpackett]

This is useful for socket activation, sandboxes/fd-passing, etc.

[ysbaddaden]

Use case is valid, but CI is red.

[straight-shoota]

Needs fix and maybe a spec for the described behaviour.

[straight-shoota]

@myfreeweb Are you still working on this?

[valpackett]

I don't understand why that test is failing..

[straight-shoota]

@myfreeweb The added TCPServer#initialize(fd) shadows TCPServer.new(port) because both can be called with a single Int32 argument.

I'd suggest to make fd an required named argument: def initialize(*, fd : Int32 ... An instance can be created using TCPServer.new(fd: fd).

This should be changed uniquely in all fd constructors.

[straight-shoota]

It's a shame that such a change breaks only one mostly unrelated SSL spec 😢

[valpackett]

Passes now

[straight-shoota]

Awesome 👍 Could you add a doc to the now public Socket#initialize as well?

[valpackett]

done

[straight-shoota]

👍