Make initializing formal access available by default

tests/language/initializing_formal_type_test.dart

 // Copyright (c) 2016, 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.
 //
 // DartOptions=--initializing-formal-access
 // VMOptions=--initializing-formal-access
 
 import "package:expect/expect.dart";
 
 class A {
-  int x;
-  String y;
-  A(this.x) : y = x { y = x; }
+  num x;
+  double y;
+  // Finding the type of an initializing formal: should cause a warning
+  // in the initializer but not the body, because the former has type
+  // `int` and the latter has type `num`.
+  A(int this.x) : y = x {
+    y = x;
+  }
 }
 
 main() {
   A a = new A(null);
   Expect.equals(a.x, null);
   Expect.equals(a.y, null);
 }