Fix test__makefile_ref on Windows using a test-time optional dependency on psutil. appveyor installs this dep.

Fix test__issues461_471 on Windows. Extensive comments about the differences in Windows signal handling inline.

I verified in a local VM that gevent's universal newline handling in subprocess matches the stdlibs (it's arguably broken). Update the tests for this case and mark them no longer failing

Make Popen.wait() raise the right exception on PY3 windows so that subprocess.call() doesn't hang if the process doesn't exit within the timeout.

It might be simple to make subprocess more-or-less work under Windows/Py3. First step is to import the moved names from the right place. Fixes #668. Fixes #669.

Maybe we don't need to include the apparently borked header after all? Hate to make changes to libev source though.

Trying latest batch magic from https://github.com/ogrisel/python-appveyor-demo/tree/master, claims 3.5 support

Also, this comes on the heels of adding back __weakref__ to Semaphore.
This becomes a field in the struct and the field is cleared in
tp_dealloc. It seems like this would trigger the memory leak bug when
taking references to a subclass, but testing seems to show that
doesn't happen. I guess PyPy handles that specially:

>>>> objgraph.show_growth()
>>>> _ = [weakref.ref(gevent.thread.LockType()) for i in range(1000)]; del _
>>>> objgraph.show_growth()
>>>>

[skip ci]