* Roll V8 back to 3.9.24.31

* build: x64 target should always pass -m64 (Robert Mustacchi)

* add NODE_EXTERN to node::Start (Joel Brandt)

* repl: Warn about running npm commands (isaacs)

* slab_allocator: fix crash in dtor if V8 is dead (Ben Noordhuis)

* slab_allocator: fix leak of Persistent handles (Shigeki Ohtsu)

* windows/msi: add node.js prompt to startmenu (Jeroen Janssen)

* windows/msi: fix adding node to PATH (Jeroen Janssen)

* windows/msi: add start menu links when installing (Jeroen Janssen)

* windows: don't install x64 version into the 'program files (x86)' folder (Matt Gollob)

* domain: Fix #3379 domain.intercept no longer passes error arg to cb (Marc Harter)

* fs: make callbacks run in global context (Ben Noordhuis)

* fs: enable fs.realpath on windows (isaacs)

* child_process: expose UV_PROCESS_DETACHED as options.detached (Charlie McConnell)

* child_process: new stdio API for .spawn() method (Fedor Indutny)

* child_process: spawn().ref() and spawn().unref() (Fedor Indutny)

* Upgrade npm to 1.1.25
- Enable npm link on windows
- Properly remove sh-shim on Windows
- Abstract out registry client and logger