We shouldn't have APIs that call Isolate::GetCurrent() internally. This
change removes all remaining occurrences of inlined methods in v8.h

BUG=none
R=svenpanne@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/85693002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18058 ce2b1a6d-e550-0410-aec6-3dcde31c8c00