Fixing many link syntaxes in doc comments

sdk/lib/io/file_system_entity.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;
 
 /**
  * The type of an entity on the file system, such as a file, directory, or link.
  *
  * These constants are used by the [FileSystemEntity] class
@@ skipping 179 matching lines @@
  *
  * Here's the exists method in action:
  *
  *     entity.exists().then((isThere) {
  *       isThere ? print('exists') : print('non-existent');
  *     });
  *
  *
  * ## Other resources
  *
- * [Dart by Example](https://www.dartlang.org/dart-by-example/#files-directories-and-symlinks)
- * provides additional task-oriented code samples that show how to use
- * various API from the [Directory] class and the [File] class,
- * both subclasses of FileSystemEntity.
+ * * [Dart by
+ *   Example](https://www.dartlang.org/dart-by-example/#files-directories-and-symlinks)
+ *   provides additional task-oriented code samples that show how to use various
+ *   API from the [Directory] class and the [File] class, both subclasses of
+ *   FileSystemEntity.
  *
- * * [I/O for Command-Line Apps](https://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html#ch03-dartio---file-and-socket-io-for-command-line-apps)
- * a section from _A Tour of the Dart Libraries_
- * covers files and directories.
+ * * [I/O for Command-Line
+ *   Apps](https://www.dartlang.org/docs/dart-up-and-running/ch03.html#dartio---io-for-command-line-apps),
+ *   a section from _A Tour of the Dart Libraries_ covers files and directories.
  *
  * * [Write Command-Line Apps](https://www.dartlang.org/docs/tutorials/cmdline/),
- * a tutorial about writing command-line apps, includes information
- * about files and directories.
-
+ *   a tutorial about writing command-line apps, includes information about
+ *   files and directories.
  */
 abstract class FileSystemEntity {
   String get path;
 
   /**
    * Returns a [Uri] representing the file system entity's location.
    *
    * The returned URI's scheme is always "file" if the entity's [path] is
    * absolute, otherwise the scheme will be empty.
    */
@@ skipping 609 matching lines @@
     return buffer.toString();
   }
 }
 
 
 class _FileSystemWatcher {
   external static Stream<FileSystemEvent> _watch(
       String path, int events, bool recursive);
   external static bool get isSupported;
 }