Classes: static should still be treated as a strict reserved word

When --harmony-classes is enabled we did not treat static as a
strict reserved word.

BUG=v8:3642
LOG=Y
R=rossberg@chromium.org

Review URL: https://codereview.chromium.org/652743009

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25087 ce2b1a6d-e550-0410-aec6-3dcde31c8c00