Optimize tgba_tba_proxy and tgba_sba_proxy for states that share
an acceptance condition on all outgoing transitions. This was motivated by experiments from Rüdiger Ehlers, showing that "ltl2ba -f 'a U (b U c)'" outperformed "ltl2tgba -f -N -R3 'a U (b U c)'". With this change and the previous one, it is no longer the case. * src/tgba/tgbatba.cc (tgba_tba_proxy_succ_iterator::aut_): Store a pointer to the source automaton and... (tgba_tba_proxy_succ_iterator::sync_): ... use it in an extra optimization step to gather the acceptance conditions common to all outgoing transitions of the destination state, and pretend they are on the current (ingoing) transition. (tgba_tba_proxy::succ_iter): Pass the source automaton to the constructed iterator. * src/tgbatest/spotlbtt.test: Test -f -N -R3 -r7. * src/tgbatest/ltl2tgba.test: Add a test case for 'a U (b U c)'.