[honu] add example of for form for iterating over lists

collects/tests/honu/for.honu

@@ -7,3 +7,7 @@ for x = 1 to 10 do {
     var y = x + 1;
     printf("x ~a y ~a\n", x, y)
 }
+
+for x in [1, 2, 3] do {
+  printf("x ~a\n", x);
+}