title: ReferenceError: GM_xmlhttpRequest is not defined
body: <p>I get a ReferenceError in the following userscript code:</p>
  
  <pre><code>// ==UserScript==
  // @name          ...
  // @namespace     ...
  // @description   ...
  // @include       ...
  // @grant         GM_xmlhttpRequest
  // ==/UserScript==
  
  console.log(GM_info);
  try
  {
      console.log(GM_xmlhttpRequest({ method: "GET", url: "http://google.ca/", synchronous: true }).readyState);
  }
  catch (e)
  {
      console.log(e);
  }
  ...
  </code></pre>
  
  <p>It first logs <code>GM_info</code> successfully, then logs the ReferenceError. (I'm using Firefox/Firebug.)</p>
  
  <blockquote>
    <p>ReferenceError: GM_xmlhttpRequest is not defined</p>
  </blockquote>
  
  <p>Why do I get this error?</p>