Progress towards Exupery 0.12

[bryce at kampjes.demon.co.uk]

All that's required is a little more debugging. This release can
compile in the background. The stress test runs again but when Exupery
starts compiling itself using the background compiler after a few
minutes it stops due to a bug. I'd like to be able to run the
background compiler for at least an hour before releasing.

Exupery is probably more reliable now than it's been before. The other
part of this release has been fixing some old stack tracing bugs. That
introduced block finder bugs which have been fixed along with some old
block finder bugs. By the standards of previous releases, it would be
releasable now.

I'm thinking about freeing up the "unused" slot in MethodContext so
that Exupery can be loaded in an image running the closure compiler
without causing crashes. More work would be required to compile
closure compiler code.

Bryce