Use SameValueZero for Map and Set

Instead of normalizing the keys we use SameValueZero for the actual
comparison.

BUG=v8:1622
LOG=Y
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/299703004

Patch from Erik Arvidsson <arv@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21400 ce2b1a6d-e550-0410-aec6-3dcde31c8c00