Change interface for enumerator_create_filter() callback

This avoids the unportable 5 pointer hack, but requires enumerating in
the callback.

src/libcharon/plugins/vici/vici_attribute.c

@@ -184,16 +184,22 @@ METHOD(attribute_provider_t, release_address, bool,
 	return found;
 }
 
-/**
- * Filter mapping attribute_t to enumerated type/value arguments
- */
-static bool attr_filter(void *data, attribute_t **attr,
-						configuration_attribute_type_t *type,
-						void *in, chunk_t *value)
+CALLBACK(attr_filter, bool,
+	void *data, enumerator_t *orig, va_list args)
 {
-	*type = (*attr)->type;
-	*value = (*attr)->value;
-	return TRUE;
+	attribute_t *attr;
+	configuration_attribute_type_t *type;
+	chunk_t *value;
+
+	VA_ARGS_VGET(args, type, value);
+
+	if (orig->enumerate(orig, &attr))
+	{
+		*type = attr->type;
+		*value = attr->value;
+		return TRUE;
+	}
+	return FALSE;
 }
 
 /**
@@ -203,7 +209,7 @@ CALLBACK(create_nested, enumerator_t*,
 	pool_t *pool, void *this)
 {
 	return enumerator_create_filter(array_create_enumerator(pool->attrs),
-									(void*)attr_filter, NULL, NULL);
+									attr_filter, NULL, NULL);
 }
 
 /**