Implement the full process interface for Windows

tests/dart/src/ProcessExitTest.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.
 //
 // Process test program to test process communication.
 
 class ProcessExitTest {
 
   static void testExit() {
-    Process process = new Process("out/Debug_ia32/process_test",
+    Process process = new Process("Debug_ia32\\process_test.exe",
                                   const ["0", "0", "99", "0"]);
 
     void exitHandler(int exitCode) {
       Expect.equals(exitCode, 99);
       process.close();
     }
 
     process.setExitHandler(exitHandler);
     process.start();
   }
 
   static void testMain() {
     testExit();
   }
 }
 
 main() {
   ProcessExitTest.testMain();
 }