Bug 907365 - Pseudo-derecursify the build (opt-in). r=gps

Also remove the compile tier added in bug 912856 when pseudo-derecursify is disabled.
Bug 907365 - Parallelize compile and tools tiers. r=gps
Bug 915648 - Parallelize make export. r=gps
Fixup for bug 915648 (sync config/recurse.mk with js/src/config)
Bug 867757 - Part 1: Allow markers to carry payload. r=aklotz

--HG--
extra : rebase_source : 31904aa5f084283bfc23ecfc53762d275967e34b
Fix window.focus() in content processes (bug 902715, r=enndeakin).
Merge m-c to inbound.
Bug 881804 (part 1) - Add support for predictive network actions. r=mcmanus f=honzab sr=biesi
Bug 881804 (part 2) - Plumb docshell into predictive network actions. r=smaug
Bug 881804 (part 3) - Plumb script loader into predictive network actions. r=jst
Bug 881804 (part 4) - Plumb layout into predictive network actions. r=bz
Bug 881804 (part 5) - Plumb image loader into predictive network actions. r=seth
Bug 881804 (part 6) - Plumb browser UI into predictive network actions to allow clearing data. r=ttaubert r=mossop f=gavin
Bug 794506 - Part 1: Move virtualenv code under mozbuild; r=ted

--HG--
rename : build/virtualenv/packages.txt => build/virtualenv_packages.txt
rename : build/virtualenv/populate_virtualenv.py => python/mozbuild/mozbuild/virtualenv.py
Bug 794506 - Part 2: Add virtualenv APIs; r=ted
Bug 917988 - Sphinx managed build system documentation; add mach build-docs; r=bsmedberg

--HG--
rename : python/mozbuild/dumbmake/README.rst => build/docs/mozbuild/dumbmake.rst
rename : python/mozbuild/mozbuild/frontend/README.rst => build/docs/mozbuild/frontend.rst
rename : python/mozbuild/README.rst => build/docs/mozbuild/index.rst
Backed out changeset 76f9cced8105 (bug 902715) for build bustage on at least Windows on a CLOSED TREE
Bug 917526 - Various duplicate symbol errors building tree with the 10.9 SDK. r=glandium
Bug 916845: Use size_t to describe length of source code in SpiderMonkey SourceHook lazy source hook. r=jorendorff
Bug 916845: Change sourceHook to a nice C++ object with a destructor. r=jorendorff