>> Smalltalk cleanUp should clean up, eh?
>
> It should clean up caches that can be recomputed when needed. Removing essential information from the image is not part of that.

My understanding is that depends on whether the aggressive option is
chosen.  According to Levente, aggressive cleaning might clean to some
unrecoverable state.  But with non-aggressive, it can be recomputed to
its prior, exact state, but with no contracts with regard to
performance.

Stubbing the ancestry falls into the latter, and it shouldn't take any
longer than opening one mcz file per package, at most.

However, I can see that my last fix to MCInfoProxy is causing an
endless recursion because I used breadthFirstAncestorsDo: in the
materialization process, which wants to put the Proxy/Info into a Set,
which requires materialization for its #hash.  It doesn't need to,
since its hash is simply the hash of its info's id, which it already
has.

I'll submit a fix.