State that this is a boolean function.
* src/tgba/succiterconcrete.hh
(tgba_succ_iterator_concrete::trans_dest_,
tgba_succ_iterator_concrete::trans_set_,
tgba_succ_iterator_concrete::trans_set_left_,
tgba_succ_iterator_concrete::neg_trans_set_): Remove.
* src/tgba/succiterconcrete.cc
(tgba_succ_iterator_concrete::tgba_succ_iterator_concrete,
tgba_succ_iterator_concrete::first): Adjust to removed members.
(tgba_succ_iterator_concrete::next): Simplify, transitions
are no labelled by boolean functions, not only conjunctions.
Suggested by Denis Poitrenaud.