move forall/2 to non_iso, correct test cases.

src/prolog/lib/non_iso.pl

@@ -0,0 +1,10 @@
+%% for builtins that are not part of the ISO standard.
+%% must be loaded at the REPL with
+
+%% ?- use_module(library(non_iso)).
+
+:- module(non_iso, [forall/2]).
+
+forall(Generate, Test) :-
+    \+ (Generate, \+ Test).
+