unfork DDC's copy of most SDK libraries

pkg/dev_compiler/tool/input_sdk/lib/core/string_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.core;
-
-abstract class StringSink {
-
-  /**
-   * Converts [obj] to a String by invoking [Object.toString] and 
-   * adds the result to `this`.
-   */
-  void write(Object obj);
-
-  /**
-   * Iterates over the given [objects] and [write]s them in sequence.
-   */
-  void writeAll(Iterable objects, [String separator = ""]);
-
-  /**
-   * Converts [obj] to a String by invoking [Object.toString] and 
-   * adds the result to `this`, followed by a newline.
-   */
-  void writeln([Object obj = ""]);
-
-  /**
-   * Writes the [charCode] to `this`.
-   *
-   * This method is equivalent to `write(new String.fromCharCode(charCode))`.
-   */
-  void writeCharCode(int charCode);
-}