autcross: simplify code using complement() and intersecting_word()
* bin/autcross.cc: Let complement() decide how to complement automata. Do not apply remove_fin(), because we have a generic emptiness check now. Use intersecting_word() instead of product()+accepting_word() so that the former can maybe be optimized in the future. * tests/core/autcross2.test: Adjust test case to use TGBA instead of monitors, as calling complement() had a side-effect of setting the "weak" property on the input.