Fix #4133, bringing the cluster worker API more in line with the
child process API.

This commit reverts the following commits (in reverse chronological order):

  74d076c errnoException must be done immediately
  ddb02b9 net: support Server.listen(Pipe)
  085a098 cluster: do not use internal server API
  d138875 net: lazy listen on handler

Commit d138875 introduced a backwards incompatible change that broke the
simple/test-net-socket-timeout and simple/test-net-lazy-listen tests - it
defers listening on the target port until the `net.Server` instance has at
least one 'connection' event listener.

The other patches had to be reverted in order to revert d138875.

Fixes #3832.

This implements server.listen({ fd: <filedescriptor> }).  The fd should
refer to an underlying resource that is already bound and listening, and
causes the new server to also accept connections on it.

Not supported on Windows.  Raises ENOTSUP.

In case a worker would spawn a new subprocess with process.env, NODE_UNIQUE_ID
would have been a part of the env. Making the new subprocess believe it is a
worker, this would result in some confusion if the subprocess where to listen to
a port, since the server handle request would then be relayed to the worker.

This patch removes the NODE_UNIQUE_ID flag from process.env on startup so any
subprocess spawned by a worker is a normal process with no cluster stuff.

Regarding discussion in #3198.  Passing the worker as an argument
to an event emitted on the worker is redundant, and an unnecessary
break in consistency vs the events on the ChildProcess objects.

It was removed from 'exit', but 'listening' and others were
overlooked.  This corrects that oversight.

test: fixes due to new cluster api.

- changed worker `death` to `exit`.
- corrected argument type expected by worker `exit` handler.

test: more tests of cluster.worker death

cluster: fixed arguments on worker 'exit' event

worker 'exit' event now emits arguments consistent with the
corresponding event in child_process module.

Fixes #2388