This will make it easier to use other STL headers in the future

Review URL: https://codereview.chromium.org/14362023

Patch from Jochen Eisinger <jochen@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14352 ce2b1a6d-e550-0410-aec6-3dcde31c8c00