This mechanism will scale to to an arbitrary number of pollable objects, so
long as they implement the MP_STREAM_GET_FILENO ioctl. Since ussl objects
pass through ioctl requests transparently to the underlying socket object,
it will allow ussl sockets to be polled. And a user object with uio.IOBase
as a base could support polling.
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
