assertion, comment.
remove visitation set from write-repr implementation.
enforce the requirement that shell commansds must be run from root dir.
special sym names now set up iteratively; special cases for VEC0 and CHAIN0 names.
make test runs test-dbg before test-rel; omit test/3-cmd dir from debug tests, since they use the wrong executable.
change order of test output diff args to be expected/actual.
improve repr printing of quoted objects.