Rename directory for back-end tests

compiler/testData/codegen/box/functions/tailRecursion/realIteratorFoldl.kt

@@ -0,0 +1,11 @@
+tailRecursive fun <T, A> Iterator<T>.foldl(acc : A, foldFunction : (e : T, acc : A) -> A) : A =
+        if (!hasNext()) acc
+        else foldl(foldFunction(next(), acc), foldFunction)
+
+fun box() : String {
+    val sum = (1..1000000).iterator().foldl(0) { (e : Int, acc : Long) ->
+        acc + e
+    }
+
+    return if (sum == 500000500000) "OK" else "FAIL: $sum"
+}