Use new library/import syntax in dart2js.

sdk/lib/_internal/compiler/implementation/dart2js.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.
 
-#library('dart2js');
+library dart2js;
 
-#import('dart:io');
-#import('dart:uri');
-#import('dart:utf');
+import 'dart:io';
+import 'dart:uri';
+import 'dart:utf';
 
-#import('../compiler.dart', prefix: 'api');
-#import('colors.dart', prefix: 'colors');
-#import('source_file.dart');
-#import('filenames.dart');
-#import('util/uri_extras.dart');
+import '../compiler.dart' as api;
+import 'colors.dart' as colors;
+import 'source_file.dart';
+import 'filenames.dart';
+import 'util/uri_extras.dart';
 
 const String LIBRARY_ROOT = '../../../../..';
 const String OUTPUT_LANGUAGE_DART = 'Dart';
 
 typedef void HandleOption(String option);
 
 class OptionHandler {
   String pattern;
   HandleOption handle;
 
@@ skipping 400 matching lines @@
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }