title: Why would one use #include_next in a project?
body: <p>To quote the iOS <a href="http://developer.apple.com/library/ios/#documentation/DeveloperTools/gcc-4.0.1/cpp/Wrapper-Headers.html">Documentation on Wrapper Headers</a>:</p>
  
  <blockquote>
    <p><code>#include_next</code> does not distinguish between &lt;file&gt; and "file" inclusion, nor does it check that the file you specify has the same
    name as the current file. It simply looks for the file named, starting
    with the directory in the search path after the one where the current
    file was found.</p>
    
    <p>The use of `#include_next' can lead to great confusion. We recommend
    it be used only when there is no other alternative. In particular, it
    should not be used in the headers belonging to a specific program; it
    should be used only to make global corrections along the lines of
    fixincludes.</p>
  </blockquote>
  
  <p>So, two questions, what is #include_next, and why would you ever need to use it?</p>