Start a node stdlib interface file

This starts the beginnings of an interface file for node built-in libraries.

I've filled in a couple of the libraries as of right now, but I've also setup the skeleton for all the others (so that it's not bottlenecked on me doing all of them, and others can help fill them in as well, piecemeal).
These opts interfaces turn out not to be very well suited for options objects... Specifically, an options object is basically just an object with a specific set of expandos that are allowed.

Any thoughts on allowing specification of optional members on an object interface definition?

(cc @avikchaudhuri @bhosmer @gabelevi )