move functions in v8::V8 that should be on v8::Isolate

R=marja@chromium.org, svenpanne@chromium.org

BUG=

Review URL: https://codereview.chromium.org/652193006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24921 ce2b1a6d-e550-0410-aec6-3dcde31c8c00