Support delegating to interfaces in ultra-light classes

compiler/testData/asJava/ultraLightClasses/delegatingToInterfaces.kt

@@ -2,6 +2,11 @@
 interface Base {
     fun printMessage()
     fun printMessageLine()
+
+    val x: Int
+    var y: Int
+
+    fun String.foo(y: Any?): Int
 }
 
 class BaseImpl(val x: Int) : Base {
@@ -9,7 +14,6 @@ class BaseImpl(val x: Int) : Base {
     override fun printMessageLine() { println(x) }
 }
 
-/** should load cls */
 class Derived(b: Base) : Base by b {
     override fun printMessage() { print("abc") }
 }