Added a version of the v8::HandleScope constructor with an Isolate and use that consistently.

I tried to limit the use of v8::Isolate::GetCurrent() and v8::internal::Isolate::Current() as much as possible, but sometimes this would have involved restructuring tests quite a bit, which is better left for a separate CL.

BUG=v8:2487

Review URL: https://codereview.chromium.org/12716010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13953 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Load/Store stub compilation refactoring.

Review URL: https://chromiumcodereview.appspot.com/12426008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13954 ce2b1a6d-e550-0410-aec6-3dcde31c8c00