Alter license comment to preserve it after Closure Compiler compilation (googlearchive#79)

Author: fritz-c

src/markerclusterer.js

@@ -17,6 +17,9 @@
  */
 
 /**
+ * @license
+ * Copyright 2010 Google Inc. All Rights Reserved.
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at