* It's unclear to me what clear-system does or should do that differs
from clear-defined-system.
  I see that clear-system is documented in asdf.texinfo, but
clear-defined-system isn't;
  furthermore, clear-defined-system doesn't appear anywhere in
quicklisp, as I can tell
  grepping through ~/quicklisp/dists/quicklisp/software after I
install all of quicklisp
  (see my repo git://common-lisp.net/users/frideau/ql-test.git for the
helpers I use).
  I believe it's the fruit of some previous fumbling with a bug, and
should be deleted,
  its contents moved to clear-system.