Display prover key checkpoint information.
See checkpoint-list for relevant background. Evaluation of
the macro call (show-checkpoint-list) prints checkpoint clauses (as
returned by checkpoint-list) as well as related information. An optional
argument has default nil; when it is not nil, then the checkpoints
are printed as untranslated terms, as described in the documentation for
checkpoint-list-pretty. Whether printed as a clause or as an
untranslated term, each checkpoint is printed with its goal-spec, i.e.,
the user-friendly goal name that one sees in prover output for a clause-identifier.
Also shown are whether or not at least one goal was forced during
the failed proof and whether the proof was aborted, and (briefly) why.