Allows KeyeLoad/KeyedStore operations where the key is a Smi to fold the untagging of the key into the element offset calculation.

Review URL: https://chromiumcodereview.appspot.com/10735020

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12156 ce2b1a6d-e550-0410-aec6-3dcde31c8c00