TransitionArray now uses <is_data_property, name, attributes> tuple as a key, which allows to have several entries for the same property name.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/661133002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25136 ce2b1a6d-e550-0410-aec6-3dcde31c8c00