Mode clean-up pt 1: rename classic/non-strict mode to sloppy mode

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/177683002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19799 ce2b1a6d-e550-0410-aec6-3dcde31c8c00