.. going to rework the listen() API to be non-blocking.

also whitespace cleanup

.. for now, the test just spins up the server and listens for messages,
echoing them back to an output port. there's a "kill" msg that it will
listen for. need to point the tcp client and server test impls at each
other for a loopback server/client test, like how its done in uv::ll

once ipv6 parse/format lands, i can add another test using the entirely
same codebase, but substituting an ip_addr ipv6 varient for the ipv4
varient used in the existing code

still need some other plumbing to get the client/server tests to work
together.

they're changed into a net::tcp::tcp_err_data record, for now. once the
scope of possible tcp errors, from libuv, is established ill create an
err type for each one and return those where they might occur