Add explicit Isolate parameter to External::New

We can't deprecate the non-Isolate version yet but soon will.

R=svenpanne@chromium.org, svenpanne@google.com
BUG=266838

Review URL: https://codereview.chromium.org/70163002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17638 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Introduce %_IsMinusZero.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/63423004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17639 ce2b1a6d-e550-0410-aec6-3dcde31c8c00