* src/tgbaalgos/closure.cc, src/tgbaalgos/closure.hh:
Add closure function.
* src/tgbaalgos/stutterize.cc, src/tgbaalgos/stutterize.hh:
Add two implementations of "self-loopize" function.
* src/tgbaalgos/Makefile.am: Add them.
* src/tgba/tgbasl.cc, src/tgba/tgbasl.hh: On-the-fly implementation of
self-loopize.
* src/tgba/Makefile.am: Add it.
* src/tgbatest/ltl2tgba.cc, src/tgbatest/stutter_invariant.test: Test
closure and sl.
* src/tgbatest/Makefile.am: Adjust.
* src/bin/ltlfilt.cc: Modify stutter-invariant option to use
automaton-based checking rather than syntactic-based checking.
* src/ltlvisit/remove_x.cc, src/ltlvisit/remove_x.hh:
Remove is_stutter_insensitive function.
* src/tgbaalgos/stutter_invariance.cc,
src/tgbaalgos/stutter_invariance.hh: Check if a formula is
stutter-invariant using closure and sl.
* wrap/python/spot.i: Add closure and sl bindings.
* bench/stutter/stutter_invariance_formulas.cc: Generate benchmarks from
given formulas.
* bench/stutter/stutter_invariance_randomgraph.cc: Generate benchmarks
from random automata.
* bench/stutter/Makefile.am: Add them.
* configure.ac: Add bench/stutter/Makefile.
* bench/Makefile.am: Add stutter subdirectory.
* README: Document bench/stutter directory.