in LBTT's statistics.

* src/tgba/tgbatba.cc (state_tba_proxy): Store an iterator,
pointing somewhere into the acceptance conditions list, instead of
an acceptance condition.
(state_tba_proxy::acceptance_iterator): New method.
(tgba_tba_proxy_succ_iterator): Adjust to use iterators too.
(tgba_tba_proxy_succ_iterator::current_state): If the current
transition is in several consecutive acceptance steps after the
expected one, advance many steps at once.
(tgba_tba_proxy::tgba_tba_proxy): Build the acceptance cycle
as a list, not a map.
(tgba_tba_proxy::get_init_state, tgba_tba_proxy::succ_iter):
Adjust.
* src/tgba/tgbatba.hh (tgba_tba_proxy::acc_cycle_): Declare as
a list, not a map.