Revert "Use symbols instead of hidden properties for i18n markers."

This reverts r24345.

TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/618123005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24346 ce2b1a6d-e550-0410-aec6-3dcde31c8c00