This has the advantage that AccessArgumentsAt itself can't deopt anymore and the
bounds check is visible for the elimination phase. Furthermore, things are
simply more consistent now, a good thing in itself. :-)

Review URL: https://codereview.chromium.org/11106012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12721 ce2b1a6d-e550-0410-aec6-3dcde31c8c00