Add a new Selector implementation for the Windows platform based on the "wepoll" library. The wepoll library provides a scalable polling interface to the Ancillary Function Driver for Winsock. The interface that it exposes is close to the Linux epoll interface. The main benefit is that the cost of selection operations are a function of the number of sockets that are ready for I/O rather than the number of channels registered with the Selector. The existing Selector on Windows uses the legacy "select" which scales horribly, partly because it is O(N) on the number of registered channels and partly because it is limited to 1024 sockets and so requires a thread per 1024 sockets.