Add a test for lazy evaluation.

programs/lazy.lily

@@ -0,0 +1,17 @@
+data IntList = { Nil, Cons(Int, IntList) }
+
+defn ones = { Cons 1 ones }
+defn zipSum l r = {
+    case l of {
+        Nil -> { 0 }
+        Cons(lv, lt) -> {
+            case r of {
+                Nil -> { 0 }
+                Cons(rv, rt) -> {
+                    (lv + rv) + zipSum lt rt
+                }
+            }
+        }
+    }
+}
+defn main = { zipSum (Cons 0 (Cons 1 Nil)) ones }