Version 3.28.71.18 (merged r24849)

Fixed mutable heap numbers leak in JSON parser.

BUG=chromium:423687
LOG=N
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/698153004

git-svn-id: https://v8.googlecode.com/svn/branches/3.28@25132 ce2b1a6d-e550-0410-aec6-3dcde31c8c00