Update library syntax in pkg files.

pkg/args/example/test_runner.dart

Index: pkg/args/example/test_runner.dart
===================================================================
--- pkg/args/example/test_runner.dart	(revision 14644)
+++ pkg/args/example/test_runner.dart	(working copy)
@@ -7,11 +7,11 @@
  * It shows what it looks like to build an [ArgParser] and then, when the code
  * is run, demonstrates what the generated usage text looks like.
  */
-#library('example');
+library example;
 
-#import('dart:io');
+import 'dart:io';
 
-#import('package:args/args.dart');
+import 'package:args/args.dart';
 
 main() {
   var parser = new ArgParser();