v8 will silently return an empty handle
which doesn't delete our data if string length is
above String::kMaxLength

Fixes: nodejs#1374
PR-URL: nodejs#2402
Reviewed-By: trevnorris - Trevor Norris <trev.norris@gmail.com>
Reviewed-By: indutny - Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: bnoordhuis - Ben Noordhuis <info@bnoordhuis.nl>

Add an optional callback parameter to `ChildProcess.prototype.send()`
that is invoked when the message has been sent.

Juggle the control channel's reference count so that in-flight messages
keep the event loop (and therefore the process) alive until they have
been sent.

`ChildProcess.prototype.send()` and `process.send()` used to operate
synchronously but became asynchronous in commit libuv/libuv@393c1c5
("unix: set non-block mode in uv_{pipe,tcp,udp}_open"), which landed
in io.js in commit 07bd05b ("deps: update libuv to 1.2.1").

Fixes: nodejs#760
PR-URL: nodejs#2620
Reviewed-By: trevnorris - Trevor Norris <trev.norris@gmail.com>
Reviewed-By: jasnell - James M Snell <jasnell@gmail.com>

This test has failed recently during a PR test in Jenkins, for
reasons seemingly not related to the change in the PR.

PR-URL: nodejs#2648
Reviewed-By: evanlucas - Evan Lucas <evanlucas@me.com>

Fixes: nodejs#1972
PR-URL: nodejs#2322
Reviewed-By: orangemocha - Alexis Campailla <orangemocha@nodejs.org>
Reviewed-By: thefourtheye - Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

These tests failed in either master builds, unrelated changes (like
marking tests as flaky) or are properly discussed in the respective
pull requests.