Backport 357e6b99ee3927cc075dd8d27c99b89d858f9dd5 from V8's upstream.

Original commit message:

  Add ScopeInfo constants to post-mortem metadata

  mdb_v8, a post-mortem debugging tool for Node.js, allows users to
  inspect ScopeInfo structures in order to get more information about
  closures.

  Currently, it hardcodes the metadata it uses to find this information.
  This change allows it to get this metadata from the node binary itself,
  and thus to adapt to future changes made to the layout of the ScopeInfo
  data structure.

  BUG=

  R=bmeurer@chromium.org

PR: #2974
PR-URL: #2974
Reviewed-By: Rod Vagg <r@va.gg>
Reviewed-By: Ben Noordhuis <ben@strongloop.com>

Notable changes

* buffer: Fixed a bug introduced in v4.1.0 where allocating a new
  zero-length buffer can result in the next allocation of a TypedArray
  in JavaScript not being zero-filled. In certain circumstances this
  could result in data leakage via reuse of memory space in
  TypedArrays, breaking the normally safe assumption that TypedArrays
  should be always zero-filled. (Trevor Norris) #2931.
* http: Guard against response-splitting of HTTP trailing headers
  added via response.addTrailers() by removing new-line ([\r\n])
  characters from values. Note that standard header values are already
  stripped of new-line characters. The expected security impact is low
  because trailing headers are rarely used. (Ben Noordhuis) #2945.
* npm: Upgrade to npm 2.14.4 from 2.14.3, see release notes for full
  details (Kat Marchán) #2958
  - Upgrades graceful-fs on multiple dependencies to no longer rely on
    monkey-patching fs
  - Fix npm link for pre-release / RC builds of Node
* v8: Update post-mortem metadata to allow post-mortem debugging tools
  to find and inspect:
  - JavaScript objects that use dictionary properties
    (Julien Gilli) #2959
  - ScopeInfo and thus closures (Julien Gilli) #2974

Notable changes

* buffer: Fixed a bug introduced in v4.1.0 where allocating a new
  zero-length buffer can result in the next allocation of a TypedArray
  in JavaScript not being zero-filled. In certain circumstances this
  could result in data leakage via reuse of memory space in
  TypedArrays, breaking the normally safe assumption that TypedArrays
  should be always zero-filled. (Trevor Norris) #2931.
* http: Guard against response-splitting of HTTP trailing headers
  added via response.addTrailers() by removing new-line ([\r\n])
  characters from values. Note that standard header values are already
  stripped of new-line characters. The expected security impact is low
  because trailing headers are rarely used. (Ben Noordhuis) #2945.
* npm: Upgrade to npm 2.14.4 from 2.14.3, see release notes for full
  details (Kat Marchán) #2958
  - Upgrades graceful-fs on multiple dependencies to no longer rely on
    monkey-patching fs
  - Fix npm link for pre-release / RC builds of Node
* v8: Update post-mortem metadata to allow post-mortem debugging tools
  to find and inspect:
  - JavaScript objects that use dictionary properties
    (Julien Gilli) #2959
  - ScopeInfo and thus closures (Julien Gilli) #2974

PR-URL: #2995