Unfortunately, arguments is pretty much the normal JS object.  For now
I am adding more sanity checks (in hope that typically arguments
list is rather short.)  However it probably requires more systematic
treatment, for example, we could optimistically copy elements until
we meet first hole and in this case resort to JS builtin.

Review URL: http://codereview.chromium.org/6062006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6256 ce2b1a6d-e550-0410-aec6-3dcde31c8c00