JS: allow to inherit external classes with overloaded functions in case we don't override them (see KT-13910).

js/js.translator/testData/box/native/overrideNativeOverloadedFunction.js

@@ -0,0 +1,5 @@
+function A() {
+}
+A.prototype.f = function(x) {
+    return typeof x;
+};