title: YUI Compressor and "use strict" hint
body: <p>I've beeing using YUI Compressor to minify JS files. I have this code: </p>
  
  <pre><code>(function(global) {
      "use strict";
  
       var X=1;
  
      /*** my code here ***/
  
  }(window));
  </code></pre>
  
  <p>And I compress it with this command: </p>
  
  <pre><code>$&gt; java -jar yuicompressor-2.4.7.jar test.js -o test.min.js --verbose
  </code></pre>
  
  <p>The "use strict" hint is not present in the compressed output file. It seems that YUI removes all hints. And it output this warning: </p>
  
  <pre><code>[WARNING] Invalid hint syntax: use strict
  (function(global){ ---&gt; "use strict" &lt;--- ;var X=1;... 
  </code></pre>
  
  <p>Although, my code works fine after compression, I'd like  to know if there is an argument to YUICompressor to preserve the hints and/or a way to avoid that warning. </p>
  
  <p>Any advice? Thanks.</p>