I really don't know how this module got left out of my last
patch, namely
  Thu Dec  2 12:35:47 GMT 2010  simonpj@microsoft.com
  * Re-jig simplifySuperClass (again)

I suggest you don't pull either the patch above, or this
one, unless you really have to.  I'm not fully confident
that it works properly yet.  Ran out of time. Sigh.