use proper notation for true, false, and null in doc comments

pkg/unittest/lib/src/configuration.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 unittest;
 
 /**
  * Describes the interface used by the unit test system for communicating the
  * results of a test run.
  */
 abstract class Configuration {
 
   /**
    * Creates an instance of [SimpleConfiguration].
    */
   factory Configuration() => new SimpleConfiguration();
 
   /**
    * Creates an [Configuration] instances that does nothing.
    *
    * For use by subclasses which wish to implement only a subset of features.
    */
   Configuration.blank();
 
   /**
-   * If [true], tests are started automatically. Otherwise [runTests]
+   * If [:true:], tests are started automatically. Otherwise [runTests]
    * must be called explicitly after tests are set up.
    */
   bool get autoStart => true;
 
   /// How long a [TestCase] can run before it is considered an error.
   /// A [timeout] value of [:null:] means that the limit is infinite.
   Duration timeout = const Duration(minutes: 2);
 
   /**
    * Called as soon as the unittest framework becomes initialized. This is done
@@ skipping 41 matching lines @@
    * Called with the result of all test cases. Browser tests commonly override
    * this to reformat the output.
    *
    * When [uncaughtError] is not null, it contains an error that occured outside
    * of tests (e.g. setting up the test).
    */
   void onSummary(int passed, int failed, int errors, List<TestCase> results,
       String uncaughtError) {}
 }