fix debugger to do well nonsource predicates.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1354 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

pl/arith.yap

@@ -63,6 +63,7 @@ do_not_compile_expressions :- set_value('$c_arith',[]).
 	).
 '$do_c_built_in'(once(G), M, ('$save_current_choice_point'(CP),NG,'$$cut_by'(CP))) :- !,
 	'$do_c_built_in'(G,M,NG).
+'$do_c_built_in'('C'(A,B.C), _, (A=[B|C])) :- !.
 '$do_c_built_in'(X is Y, _, P) :-
 	nonvar(Y),		% Don't rewrite variables
 	!,

pl/debug.yap

@@ -419,8 +419,10 @@ debugging :-
 	'$do_spy'(Cl, M, CP, InControl).
 '$spycall'(G, M, InControl) :-
 	% I lost control here.
-	'$continue_debugging'(InControl,G,M),
-	'$execute_nonstop'(G, M).
+	CP is '$last_choice_pt',
+	'$static_clause'(G,M,C,R),
+	'$continue_debugging'(InControl, G, M),
+	'$execute_clause'(G, M, R, CP).
 
 '$trace'(P,G,Module,L) :-
 	flush_output(user_output),