Turn ToNumberStub into a hydrogen code stub.

R=danno@chromium.org, hpayer@chromium.org

Review URL: https://codereview.chromium.org/19793005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15814 ce2b1a6d-e550-0410-aec6-3dcde31c8c00