Refactor CallICStub to use a different stub for each customization.

This gives us much more room to customize on different functions, by
using MajorKey to differentiate them.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/295383004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21564 ce2b1a6d-e550-0410-aec6-3dcde31c8c00