idempotency testing on real-life examples, i.e. checks that brittany(x) is
equal to brittany(brittany(x)) for some x's. The idea is that these testcases
are not yet transformed, i.e. that x is not brittany(x). This can capture
certain bugs that are not detected by checking that brittany behaves as
identity on "well-formed" input.

to run:

- put a "brittany" executable into this directory.
- cd into this directory.
- ./run.sh

report.txt will contain the results.

note that only the configuration in brittany.yaml is tested, which contains
the default settings. ideally this would be managed in some other, more
transparent fashion.