Windows control port defaults to localhost:8765

To ease testing of the windows code on unix, I implemented unix
simulation of what happens on windows, particularly of what happens when
you try to listen() on a path (an error is thrown). Some tests depend on
unix support, they are now skipped conditionally depending on the
platform.

/to @Schoonology After this, two tests still fail, ones having to do with subtleties of cluster worker signal handling, and it doesn't really surprise me that there is a platform dependency there. I don't have time to trace down why on windows right now, though.