Hi Eliot, thanks a lot for your help on the CM header.  I decided to
try to add a new bit indicator in my CompiledMethodBuffer (pickled
state of a CM) to indicate which header format it was pickled in so I
can hopefully maintain a heterogeneous environment.

Now, maybe I goofed up my image while testing it at some point because
I cannot seem to allocate a 50MB ByteString (even though (Smalltalk
vmParameterAt: 3) reports just 89,627,904)

   String new: 50000000

causes a failure in primitve 71, which causes the failure code to run,
which sends #growMemoryByAtLeast: to Smalltalk.  But, there are no
implementors of #growMemoryByAtLeast: in the image..!

Do you have an impl. of that method?  This could be a real problem for
me to move to Spur because I absolutely depend on handling OutOfMemory
errors to build my large models..