Expose JSON parser through V8 API

BUG=v8:2821
TEST=cctest/test-api/JSONParse
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/21959003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16048 ce2b1a6d-e550-0410-aec6-3dcde31c8c00