Poller enters infinite loop at EOF

LiteCore has overlooked the fact that a socket read operation will return 0 when it reaches the end of the stream, and continue to do so forever. The socket read operation needs to take this into account, and not schedule itself again in this event. Instead in the event of EOF on a read call, LiteCore should either initiate a close (if EOF write has not been recorded) or close the socket right then and there (if EOF write has been recorded).