* src/tgba/bdddict.hh, src/tgba/bdddict.cc: Store variable types and
associated formula in a vector indexed by BDD variable numbers,
instead of using several maps.
* src/evtgbaalgos/tgba2evtgba.cc, src/tgba/bddprint.cc,
src/tgba/formula2bdd.cc, src/tgbaalgos/ltl2tgba_fm.cc,
src/tgbaalgos/save.cc: Adjust usage.