title: In Emacs, what does this error mean? "Warning: cl package required at runtime"
body: <p>I am byte-compiling a module.  It gives me this warning:</p>
  
  <pre><code> Warning: cl package required at runtime
  </code></pre>
  
  <p>Why is this a warning? I am well aware that I am using the <code>cl</code> package.  In fact there is a <code>(require 'cl)</code> statement in the module.  </p>
  
  <p>Is there something wrong with using the <code>cl</code> stuff? </p>
  
  <p>If so, is there a list of published workarounds?  The main things I use are <code>mapcan</code> and <code>delete-duplicates</code>. </p>