Commit bda40a5f introduced a subtle bug where nm_minato was being
increased in more cases causing some non-deterministic automata to be
incorrectly tagged as deterministic automata.

Fixes issue #575, reported by Dávid Smolka.

* spot/twaalgos/simulation.cc (create_edges): Do not increment
nm_minato when dest is bddfalse.
* tests/core/568.test: Add Dávid's first test-case.
* tests/python/forq_contains.py: Add Dávid's second test-case.