title: How to use Clang CompilerInstance for completion?
body: <p>I have a library which uses and exposes a clang::CompilerInstance.
  How can I use the CompilerInstance for getting code-completion- suggestions ?</p>
  
  <p>Basically I'm looking to write a function with the following signature:</p>
  
  <pre><code>vector&lt;string&gt; completeSnippet(
    clang::CompilerInstance CI, 
    string codeSnippet,
    int completeAtIndex
  );
  </code></pre>
  
  <p>Any ideas ?</p>
  
  <p>Thanks in advance</p>