What is the "QTL" library?
<p>In a question about forward declaring templates, and an answer that this is not possible doing manually for standard templates, a commenter says</p>

<blockquote>
  <p>That's why I prefer QTL - I can write forward declaration for any template.</p>
</blockquote>

<p>What is that "QTL"? I have never heard about it and google doesn't come up with something useful for me.</p>
