matches the behavior of Safari and Firefox. Our old behavior was to
throw a stack overflow exception.

BUG=crbug.com/70334
TEST=mjsunit/cyclic-error-to-string.js

Review URL: http://codereview.chromium.org/6261018

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6428 ce2b1a6d-e550-0410-aec6-3dcde31c8c00