* include/vaucanson/automata/implementation/iterators/delta_transition_iterator.hh,
* include/vaucanson/automata/implementation/iterators/delta_transition_iterator.hxx,
* include/vaucanson/automata/implementation/iterators/rdelta_transition_iterator.hh,
* include/vaucanson/automata/implementation/iterators/rdelta_transition_iterator.hxx:
Use const graph_t& instead of graph_t.  The iterators now work
with bmig.