Revert "Turn old space cons strings into regular external strings (not short)."

This reverts commits r22192 and r22194.

TBR=hpayer@chromium.org

Review URL: https://codereview.chromium.org/367113003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22195 ce2b1a6d-e550-0410-aec6-3dcde31c8c00