Updates dartc to recognize 'default' keyword on interface and updated factory method syntax

tests/stub-generator/src/MintMakerPromiseWithStubsTest-generatedTest.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.
 
 // IsolateStubs=MintMakerPromiseWithStubsTest.dart:Mint,Purse
 
 #library("MintMakerPromiseWithStubsTest-generatedTest");
 #import("../../isolate/src/TestFramework.dart");
 
 /* class = Mint (tests/stub-generator/src/MintMakerPromiseWithStubsTest.dart/MintMakerPromiseWithStubsTest.dart: 10) */
@@ skipping 115 matching lines @@
 
   void main() {
     this.port.receive(void _(var message, SendPort replyTo) {
       Purse thing = new Purse();
       SendPort port = Dispatcher.serve(new Purse$Dispatcher(thing));
       Proxy proxy = new Proxy.forPort(replyTo);
       proxy.send([port]);
     });
   }
 }
-interface Mint factory MintImpl {
+interface Mint default MintImpl {
 
   Mint();
 
   Purse createPurse(int balance);
 
 }
 
-interface Purse factory PurseImpl {
+interface Purse default PurseImpl {
 
   Purse();
 
   int queryBalance();
   Purse sproutPurse();
   Promise<int> deposit(int amount, Purse$Proxy source);
 
 }
 
 class MintImpl implements Mint {
@@ skipping 91 matching lines @@
       expect.succeeded();
       print("##DONE##");
     });
   }
 
 }
 
 main() {
   runTests([MintMakerPromiseWithStubsTest.testMain]);
 }