leads to stack corruption in 32-bit version of V8.

See http://code.google.com/p/chromium/issues/detail?id=27227 for a
reproducible case.

Since this is only an issue on 32-bit V8 I think this has got
something to do with the UnsafeSmi handling that we do on ia32.  I'm
reverting for now so we can push a fix, but we should track down the
issue and create a regression test for this.

Review URL: http://codereview.chromium.org/383005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3263 ce2b1a6d-e550-0410-aec6-3dcde31c8c00