ReferenceError.prototype.__proto__ which will make "error instanceof
Error" fail. However, the ReferenceError.prototype object itself
cannot be modified. Therefore, the error checks must check for
concrete error instances instead of only checking for Error.

Review URL: http://codereview.chromium.org/6388003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6450 ce2b1a6d-e550-0410-aec6-3dcde31c8c00