FIXED: retract/1 issues due to module qualification

This addresses #1125.

src/lib/builtins.pl

@@ -998,14 +998,14 @@ retract_clause(Head, Body) :-
 
 :- meta_predicate retract(0).
 
-retract(Clause) :-
+retract(Clause0) :-
-    (  Clause \= (_ :- _) ->
+    strip_module(Clause0, Module, Clause),
-       Head = Clause,
+    (   Clause = (Head :- Body) ->
-       Body = true,
+        true
-       retract_clause(Head, Body)
+    ;   Head = Clause,
-    ;  Clause = (Head :- Body) ->
+        Body = true
-       retract_clause(Head, Body)
+    ),
-    ).
+    retract_clause(Module:Head, Body).
 
 
 :- meta_predicate retractall(0).