Strip useless acceptance conditions in scc_filter().
A useless acceptance conditions is one that is always implied by another. * src/misc/bddop.hh, src/misc/bddop.cc (compute_neg_acceptance_conditions): New function. * src/tgba/tgbaexplicit.hh, src/tgba/tgbaexplicit.cc (set_acceptance_conditions): New function. * src/tgbaalgos/scc.cc (build_map, build_scc_stats, dump_scc_dot): Keep track of useful acceptance conditions. (useful_acc_of): New function. * src/tgbaalgos/scc.hh (scc_stats, scc_map::scc::useful_scc): New attributes. * src/tgbaalgos/sccfilter.cc (filter_iter): Adjust to filter useless acceptance conditions. (scc_filter): Compute useful acceptance conditions and pass them to filter_iter.