Remove buggy ToNumber truncation

BUG=v8:2813
R=danno@chromium.org

Review URL: https://codereview.chromium.org/21531003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16008 ce2b1a6d-e550-0410-aec6-3dcde31c8c00