Added tests on class delegation

backend.native/tests/codegen/classDelegation/method.kt

@@ -0,0 +1,19 @@
+interface A<T> {
+    fun foo(): T
+}
+
+class B : A<String> {
+    override fun foo() = "OK"
+}
+
+class C(a: A<String>) : A<String> by a
+
+fun box(): String {
+    val c = C(B())
+    val a: A<String> = c
+    return c.foo() + a.foo()
+}
+
+fun main(args: Array<String>) {
+    println(box())
+}