bin: add a --check option for automata outputs

This currently only allows extra check for stutter invariance.

* src/bin/common_aoutput.cc: Add check option,
and test stutter invariance.
* src/twaalgos/stutter.cc, src/twaalgos/stutter.hh
(check_stutter_invariance): New function.
* src/tests/stutter-tgba.test: Test it.

src/tests/stutter-tgba.test

@@ -70,4 +70,11 @@ State: 2
 --END--
 EOF
 
+run 0 $ltl2tgba -H 'F(a & X(!a & b))' > input
+grep stutter-invariant input && exit 1
+run 0 $ltl2tgba --check=stutter 'F(a & X(!a & b))' > input.2
+grep stutter-invariant input.2
+run 0 $autfilt --check=stutter input > input.2
+grep stutter-invariant input.2
+
 diff output expected