Reland "Load global object and builtins from activation."

Reland fixes:
Don't set string flags (doing so leaks memory).

Load closure from activation for building literals.

R=titzer@chromium.org

Review URL: https://codereview.chromium.org/484273003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23275 ce2b1a6d-e550-0410-aec6-3dcde31c8c00