Add a script that can generate simple test cases for user-exposed JS builtins

(we won't check in any such tests; they can be generated on the fly when needed)

R=mbarbella@chromium.org

Review URL: https://codereview.chromium.org/554683002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23862 ce2b1a6d-e550-0410-aec6-3dcde31c8c00