Adding tgba-based stutter-invariance checking

* 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.

src/tgbaalgos/Makefile.am

@@ -29,6 +29,7 @@ tgbaalgosdir = $(pkgincludedir)/tgbaalgos
 
 tgbaalgos_HEADERS = \
   bfssteps.hh \
+  closure.hh \
   complete.hh \
   compsusp.hh \
   cycles.hh \
@@ -69,6 +70,8 @@ tgbaalgos_HEADERS = \
   simulation.hh \
   stats.hh \
   stripacc.hh \
+  stutter_invariance.hh \
+  stutterize.hh \
   tau03.hh \
   tau03opt.hh \
   translate.hh \
@@ -77,6 +80,7 @@ tgbaalgos_HEADERS = \
 noinst_LTLIBRARIES = libtgbaalgos.la
 libtgbaalgos_la_SOURCES = \
   bfssteps.cc \
+  closure.cc \
   complete.cc \
   compsusp.cc \
   cycles.cc \
@@ -117,6 +121,8 @@ libtgbaalgos_la_SOURCES = \
   simulation.cc \
   stats.cc \
   stripacc.cc \
+  stutter_invariance.cc \
+  stutterize.cc \
   tau03.cc \
   tau03opt.cc \
   translate.cc \