Our topological sort code really deserves a function of its own.
Additionally, don't print from inside the topological sort code:
instead, return a result, and let the caller print it.
I'll want to make this block into a series of functions in a
subsequent commit, but I'm doing this separately to get the
indentation change out of the way.
This branch will end up with making checkIncludes.py an integrated
part of practracker, for ticket 31176.
Includes configuration files to enforce these rules on lib and
common. Of course, "common" *is* a modularity violation right now,
so these rules aren't as strict as I would like them to be.
