Make Map::Create always use the Object function, and remove the unused inobject properties

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/584943002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24094 ce2b1a6d-e550-0410-aec6-3dcde31c8c00