This change should fix the Windows issues Qt Creator has been having, by
ensuring accept() and accept4() work in O_NONBLOCK mode. I switched away
from AcceptEx() which is buggy, back to using WSAAccept(). This requires
making a tradeoff where we have to accept a busy loop. However it is low
latency in nature, just like our new and improved Windows poll() code. I
was furthermore able to eliminate a bunch of Windows-related test todos.
