10" or "b != 3".  This only work for integer variables presently.

* iface/dve2/dve2.hh (load_dve2): Take an atomic_prop_set
argument to indicate the AP to observe.
* iface/dve2/dve2.cc (convert_aps): New function.  Parse the
atomic propositions in format them in a prop_set structure that
will allow fast generation of the state condition.
(load_dve2): Call convert_aps, and pass the resulting prop_set
structure to the kripke object.
(dve2_kripke::dve2_kripke): Store the prop_set structure.
(dve2_kripke::~dve2_kripke): Release the prop_set, and unregister
the bdd_variable associated to it.
(compute_state_condition): New method that uses the prop_set.
(succ_iter, state_condition): Call compute_state_condition().
* iface/dve2/dve2check.cc: Adjust the call to load_dve2 to
pass it atomic propositions read from the command line.