kt-1760 delegation to java iface:

- removed codegen's unnecessary lookup for a declaration
- skipped class' only supertype (if any) methods when delegating

compiler/testData/codegen/classes/delegationJava.kt

@@ -0,0 +1,13 @@
+class TestJava(r : Runnable) : Runnable by r {}
+class TestRunnable() : Runnable {
+  public override fun run() = System.out.println("foobar")
+}
+
+fun box() : String {
+    var del = TestJava(TestRunnable())
+    del.run()
+    if (del !is Runnable)
+        return "Fail #1"
+
+    return "OK"
+}

compiler/testData/diagnostics/tests/DelegationToJavaIface.kt

@@ -0,0 +1,3 @@
+class TestIface(r : Runnable) : Runnable by r {}
+
+class TestObject(o : Object) : <!DELEGATION_NOT_TO_TRAIT!>Object<!> by o {}