* src/tgbaalgos/ltl2tgba_fm.hh, src/tgbaalgos/ltl2tgba_fm.cc
(ltl_to_tgba_fm): Add a new option "containment_checks" to enable some language containment checks (via emptiness checks) during the translation. This first attempt currently only use containment checks to merge states bisimulating each other. * src/tgbatest/ltl2tgba.cc: Bind this to option "-c". * src/tgbatest/spotlbtt.test: Check it.