Use InternalArray in Object.defineProperties to avoid issues with overwriten properties on Array.prototype

TEST=mjsunit/regress/regress-1625
BUG=v8:1625
Review URL: http://codereview.chromium.org/7631039

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8964 ce2b1a6d-e550-0410-aec6-3dcde31c8c00