Remove legacy syntax support for library import

tests/standalone/package/packages/lib3/sub/lib3.dart

Index: tests/standalone/package/packages/lib3/sub/lib3.dart
===================================================================
--- tests/standalone/package/packages/lib3/sub/lib3.dart	(revision 20447)
+++ tests/standalone/package/packages/lib3/sub/lib3.dart	(working copy)
@@ -2,9 +2,9 @@
 // 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('lib3');
+library lib3;
 
-#import('package:shared.dart');
+import 'package:shared.dart';
 
 void lib3() {
   output += '|lib3';