child_process: support options in send()

This commit adds an options object to process.send(). The same
object is propagated to process._send(), the _handleQueue, and the
send() and postSend() functions of the handle converter.

Fixes: https://github.com/nodejs/node/issues/4271
PR-URL: https://github.com/nodejs/node/pull/5283


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>