Fix various inheritance bugs

tests/language/field7a_negative_test.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-// Dart test to catch error reporting bugs in class fields declarations.
-// Should be an error because we have a function overriding a setter name.
-
-class A {
-  void set a(var val) {
-    int i = val;
-  }
-  int a() {
-    return 1;
-  }
-}
-
-class Field7aNegativeTest {
-  static testMain() {
-  }
-}
-
-main() {
-  Field7aNegativeTest.testMain();
-}