added a helper method for converting functions into iterators (which have all the various standard library APIs on them)

libraries/stdlib/test/iterators/FunctionIteratorTest.kt

@@ -0,0 +1,22 @@
+package iterators
+
+import kotlin.*
+import kotlin.test.*
+import kotlin.util.*
+
+import org.junit.Test
+
+class FunctionIteratorTest {
+
+    Test fun iterateOverFunction() {
+        var count = 3
+
+        val iter = iterate<Int> {
+            count--
+            if (count >= 0) count else null
+        }
+
+        val list = iter.toList()
+        assertEquals(arrayList(2, 1, 0), list)
+    }
+}