* spot/twaalgos/stutter.cc,
spot/twaalgos/stutter.hh (check_stutter_invariance): Add a
find_counterexamples argument.
* spot/twaalgos/hoa.cc: Output accepted-word and rejected-word examples.
* bin/common_aoutput.cc: Handle --check=stutter-sensitive-example.
* NEWS: Mention it.
* tests/core/stutter-tgba.test: Test it.
* doc/org/concepts.org, doc/org/hoa.org: Document accepted-word and
rejected-word named properties.
* bin/man/spot-x.x: Mention that --check=stutter-sensitive-example
ignores SPOT_STUTTER_CHECK.