Clear normalized map caches in all global contexts not just in those reachable from ThreadLocalTops.

Issue reported by Mark Lam <mark.lam@palm.com> from Hewlett-Packard Development Company, LP.

Review URL: http://codereview.chromium.org/3828011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5654 ce2b1a6d-e550-0410-aec6-3dcde31c8c00