title: How to add a menu in [ctrl] popup menu of a method?
body: <p>I don't know how to describe is exactly......</p>
  
  <p>Er, you know, when you press [ctrl] and move your mouse over a method name, there is a popup menu like this:</p>
  
  <pre><code>==========
  Open Declaration
  Open Implementation
  Open Return Type
  ========
  </code></pre>
  
  <p>Now I want to add my own actions here, but I didn't find where to write these code even I grep "Open Return Type" in JDT source.</p>
  
  <p>Anyone has an idea? Thanks!</p>