Turn FastNewContextStub into a HydrogenCodeStub.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/145513002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18764 ce2b1a6d-e550-0410-aec6-3dcde31c8c00