twagraph: fix highlight-edges in defrag_states
Fixes #555 (closed) reported by Dávid Smolka.
- spot/twa/twagraph.cc (defrag_states): Update highlight-edge.
- spot/graph/graph.hh (defrag_states): Just point to twa_graph::defrag_states in a comment, because the latter relies on the implementation detail of graph::defrag_state.
- tests/python/parsetgba.py: Add test case.
- NEWS Mention the bug.