We use the UV_HANDLE_BOUND flag to mark a socket as bound to a
port. We need to do this for sockets that are sent from another
process as well as sockets that created by the process itself.
First check if the port number is non-zero. If yes then mark
it as bound.
PR-URL: https://github.com/libuv/libuv/pull/1348
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>