* 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.