Use relative URIs for core library part-of statements.

sdk/lib/io/io_sink.dart

 // Copyright (c) 2013, 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.
 
-part of dart.io;
+part of "io.dart";
 
 /**
  * A combined byte and text output.
  *
  * An [IOSink] combines a [StreamSink] of bytes with a [StringSink],
  * and allows easy output of both bytes and text.
  *
  * Writing text ([write]) and adding bytes ([add]) may be interleaved freely.
  *
  * While a stream is being added using [addStream], any further attempts
@@ skipping 304 matching lines @@
 
   void writeln([Object object = ""]) {
     write(object);
     write("\n");
   }
 
   void writeCharCode(int charCode) {
     write(new String.fromCharCode(charCode));
   }
 }