The commit "Cube-E: fix especially the Comm Toolbox" placed some changes
to System.make in source.patch. Changes to makefiles should go in
build-system.patch. Never mind that System.make is created from whole
cloth and cannot have meaningful changes anyway.
The automated changes to the output of git-format-patch looked okay, but
they were swallowing up binary changes. Now they are more conservative
and hopefully more robust. As an exception, hashes are still removed for
non-binary diffs.
For debugging, `scripts/flatten` now has a `--raw` option to skip this
post-processing step.
Soon I should try to stabilise the patch format.
