title: INCLUDEPATH in qmake project file doesn't work
body: <p>I've got a problem with include in a qmake project. In my .pro file I've got:</p>
  
  <pre><code>INCLUDEPATH += "C:\OpenCV\build\include"
  </code></pre>
  
  <p>and in my cpp : </p>
  
  <pre><code>#include &lt;opencv\cv.h&gt;
  </code></pre>
  
  <p>The compiler indicates an error: </p>
  
  <blockquote>
    <p>Cannot open include file: 'opencv\cv.h': No such file or directory</p>
  </blockquote>
  
  <p>but if I write this in my cpp:</p>
  
  <pre><code>#include "C:\OpenCV\build\include\opencv\cv.h"
  </code></pre>
  
  <p>it works!</p>
  
  <p>I build the project from within Qt Creator. What am I doing wrong?</p>