fix(parser)

parser used to work depending on opening parenthesis and therefore
parsed e.g. `(if 0 (list 1 2 3) 1)` as two seperate expressions, thus
the example would print:
1
(1 2 3)

Now fixed by using a stack for parenthesis

builtins.c

@@ -38,14 +38,14 @@ func_arithmetic(lisp_function_gt_eq, >=);
 int lisp_function_println(Nodes *args, Scopes *scopes, Node *result) {
     if (args->count != 1) {
         printf("'+' expects one argument!\n");
-        return 0;
+        return 1;
     }
 
     eval_one(args->items[0], scopes, result);
     node_print(*result);
     printf("\n");
 
-    return 1;
+    return 0;
 }
 
 int lisp_function_list(Nodes *args, Scopes *scopes, Node *result) {