CompState now contains Sets and Maps, which aren't instances of Data and thus
break pshow. This could be fixed in the future by providing instance
definitions, assuming the GHC library maintainers don't beat us to it.
The compiler itself is under the GPLv2+; the support code that gets built into
user programs is under the LGPLv2+. This matches the existing practice for the
KRoC project.
(As with Occade, I've used the new GPLv3-style license header in the source
files, though, since that avoids having to update the FSF's postal address.)
