intercept:nb_intercept

As intercept_all/4, but backtracing inside Goal does not reset List. Consider this program and the subsequent queries

enum_b(F, T) :- forall(between(F, T, I), send_signal(emit(I))).

?- intercept_all(I, enum_b(1, 6), emit(I), List).
List = [].

?- nb_intercept_all(I, enum_b(1, 6), emit(I), List).
List = [1, 2, 3, 4, 5, 6].