2016-01-19, Version 4.2.5 "Argon" (LTS) Release

Notable changes:

* assert
  -  accommodate ES6 classes that extend Error (Rich Trott) #4166
* build
  - add "--partly-static" build options (Super Zheng) #4152
* deps
  - backport 066747e from upstream V8 (Ali Ijaz Sheikh) #4655
  - backport 200315c from V8 upstream (Vladimir Kurchatkin) #4128
  - upgrade libuv to 1.8.0 (Saúl Ibarra Corretgé)
* docs
  - various updates landed in 70 different commits!
* repl
  - attach location info to syntax errors (cjihrig) #4013
  - display error message when loading directory (Prince J Wesley) #4170
* tests
  - various updates landed in over 50 commits
* util
  - allow lookup of hidden values (cjihrig) #3988