When running Exupery's test suite it crashes every few runs.
With a bad (freshly created) image it can crash every single time
that TestExuperyPlugin>>testBasicRememberSetsBothOld is run. When
the image is first created the other remembered set tests also
cause it to crash. Images get more reliable with time.

With my fix I've run that test for well over a minute continuously
without a single crash. That test takes a third of a second so that's
over 200 times successfully.

Interestingly, the first time I run that method with the fixed VM it
crashes. If I run any other test first, it is then stable.

I can easily reproduce these crashes with the Exupery development
image when running Exupery's test suite. The reason I'm investigating
is a new image I created was crashing every time I ran that test. My
older development image only crashes ever couple of test runs. The
problem is subtle, add a few extra expressions and it will go away.

For me, for now, that fix is enough to be able to produce an image to
go with the next Exupery release. Without that fix, a newly created
image will crash every time the test suite is run. If the troublesome
methods are commented and the test suite is run a few times then it
those tests will pass sometimes but they still crash the VM every few
runs. It would be nice to get a proper fix though.

Bryce