Remove hole handling since holes cannot occur in JSObjects anymore.
The only case in which the hole can still occur, is in a pre-allocated PropertyCell in a GlobalObject. In that case it indicates that the property is absent.

BUG=
R=ishell@chromium.org

Review URL: https://codereview.chromium.org/389353002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22441 ce2b1a6d-e550-0410-aec6-3dcde31c8c00