Change core lib, dart2js, and more for new optional parameters syntax

pkg/args/lib/args.dart

 // Copyright (c) 2012, 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.
 
 /**
  * This library lets you define parsers for parsing raw command-line arguments
  * into a set of options and values using [GNU][] and [POSIX][] style options.
  *
  * ## Defining options ##
  *
@@ skipping 542 matching lines @@
   final List allowed;
   final defaultValue;
   final Function callback;
   final String help;
   final Map<String, String> allowedHelp;
   final bool isFlag;
   final bool negatable;
   final bool allowMultiple;
 
   _Option(this.name, this.abbreviation, this.help, this.allowed,
-      this.allowedHelp, this.defaultValue, this.callback, [this.isFlag,
-      this.negatable, this.allowMultiple = false]);
+      this.allowedHelp, this.defaultValue, this.callback, {this.isFlag,
+      this.negatable, this.allowMultiple: false});
 }
 
 /**
  * Takes an [ArgParser] and generates a string of usage (i.e. help) text for its
  * defined options. Internally, it works like a tabular printer. The output is
  * divided into three horizontal columns, like so:
  *
  *     -h, --help  Prints the usage information
  *     |  |        |                                 |
  *
@@ skipping 201 matching lines @@
       allowedBuffer.add(allowed);
       if (allowed == option.defaultValue) {
         allowedBuffer.add(' (default)');
       }
       first = false;
     }
     allowedBuffer.add(']');
     return allowedBuffer.toString();
   }
 }