#857 net.server: API for watching an arbitrary file descriptor
In cases where we want to keep track of events from other things that communicate
via 'readyness' of an FD, not having to wrap this in a socket-like API would be helpful.
server.watchfd(fd : number, onreadable : callback, onwritable : callback) -> handle object
The presence of either callback would be used to determine what events to watch for.