Add test to check that Function.caller must not expose native functions.

R=svenpanne@chromium.org
BUG=v8:105

Review URL: https://chromiumcodereview.appspot.com/13166002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14096 ce2b1a6d-e550-0410-aec6-3dcde31c8c00