2015-10-12, Version 4.2.0 'Argon' (LTS) Release

The first Node.js LTS release! See https://github.com/nodejs/LTS/
for details of the LTS process.

* **icu**: Updated to version 56 with significant performance improvements
  (Steven R. Loomis) https://github.com/nodejs/node/pull/3281
* **node**:
  - Added new `-c` (or `--check`) command line argument for checking script
    syntax without executing the code (Dave Eddy) https://github.com/nodejs/node/pull/2411
  - Added `process.versions.icu` to hold the current ICU library version
    (Evan Lucas) https://github.com/nodejs/node/pull/3102
  - Added `process.release.lts` to hold the current LTS codename when the
    binary is from an active LTS release line (Rod Vagg) https://github.com/nodejs/node/pull/3212
* **npm**: Upgraded to npm 2.14.7 from 2.14.4, see release notes:
  https://github.com/npm/npm/releases/tag/v2.14.7 for full details (Kat Marchán) https://github.com/nodejs/node/pull/3299

PR-URL: https://github.com/nodejs/node/pull/3258