Add Windows backend for IO completion ports (iocp)

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Suggestion from Mario.

Research URLs:

   * http://en.wikipedia.org/wiki/Input/output_completion_port
   * http://msdn.microsoft.com/en-us/library/aa365198%28VS.85%29.aspx
   * http://code.google.com/p/pyiocp/
   * http://posted-stuff.blogspot.com/2009/07/iocp-based-sockets-with-ctypes-in.html
   * http://posted-stuff.blogspot.com/2009/07/iocp-based-sockets-with-ctypes-in_22.html
   * http://posted-stuff.blogspot.com/2009/07/iocp-based-sockets-with-ctypes-in_24.html

NOTE Twisted appears to have support but that approach is unlikely to mix with 
the pyevent model.

Original issue reported on code.google.com by clac...@gmail.com on 23 Dec 2011 at 8:24