included in the compiled files. (also, misc minor cleanups
notably a new exercise in tut.scrbl)
closes PR 12547 --- there are still a few uses left, but they do not
seem to be coming from Redex proper:
- /Users/robby/git/plt/collects/racket/private/map.rkt still appears
in a bunch of places (there is a separate PR for that I believe),
and
- /Users/robby/git/plt/collects/redex/../private/reduction-semantics.rkt
appears in tl-test.rkt, but I do not see how it
is coming in via Redex code, so hopefully one of the other
PRs that Eli submitted is the real cause. If not, I'll revisit later
