ltlcross: adjust to work with generic acceptance

* src/bin/ltlcross.cc: Remove Fin-acceptance before
doing checks.  More --verbose output.
* src/tgba/acc.cc, src/tgba/acc.hh: Add an eval_sets() function
to find the set of acceptance sets needed to satisfy the condition
in an accepting SCC.
* src/tgbaalgos/gtec/ce.cc: Use eval_sets() when computing
a counter example.
* src/tgbaalgos/gtec/gtec.cc: Raise an exception when called
on an acceptance that contains Fin.
* src/tgbatest/ltl2dstar3.test, src/tgbatest/ltlcrossce2.test:
New files.
* src/tgbatest/Makefile.am: Add them.
* src/tgba/tgba.cc (is_empty): Call remove_fin if needed.
* src/tgbaalgos/product.cc, src/tgbaalgos/dtgbacomp.cc: Adjust
to work with generic acceptance.

src/tgbatest/Makefile.am

@@ -109,6 +109,7 @@ TESTS = \
   ltlcross4.test \
   ltl2dstar.test \
   ltl2dstar2.test \
+  ltl2dstar3.test \
   ltl2ta.test \
   ltl2ta2.test \
   randaut.test \
@@ -121,6 +122,7 @@ TESTS = \
   emptchke.test \
   dfs.test \
   ltlcrossce.test \
+  ltlcrossce2.test \
   emptchkr.test \
   ltlcounter.test \
   basimul.test \