Whenever >>> produces a non-smi result, the binary op stub would
return a wrong result in case of a failed new-space allocation.

This also fixes the (flaky) sparse-array-reverse test which was failing
sometimes because of this.

BUG=v8:1359
TEST=mjsunit/sparse-array-reverse.js
Review URL: http://codereview.chromium.org/6927013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7790 ce2b1a6d-e550-0410-aec6-3dcde31c8c00