ES6: Make sure we do not store -0 as the key in Map/Set

BUG=v8:3515
LOG=Y
R=adamk@chromium.org, dslomov@chromium.org

Review URL: https://codereview.chromium.org/478683002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23204 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Load global object and builtins from activation.

BUG=
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/474633003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23205 ce2b1a6d-e550-0410-aec6-3dcde31c8c00