als2::dummy_mutex</a></code>.  The motivation for providing
      <code class="computeroutput"><a class="link" href="../boost/signals2/mutex.html" title="Class mutex">boost::signals2::mutex</a></code> is simply that the <code class="computeroutput">boost::mutex</code>
      class provided by the Boost.Thread library currently requires linking to libboost_thread.
      The <code class="computeroutput"><a class="link" href="../boost/signals2/mutex.html" title="Class mutex">boost::signals2::mutex</a></code> cl