title: boost::lock does not compile in boost 1.53
body: <p>I am compiling a project. It has the following lines : </p>
  
  <pre><code>boost::mutex::scoped_lock ml(m_meta_mut, boost::defer_lock);
      boost::mutex::scoped_lock tl(m_tables_mut, boost::defer_lock);
      boost::lock(ml, tl);
  </code></pre>
  
  <p>I am getting <code>lock is not a member of boost</code> on the third line. I am using boost1.53 (the project recommends 1.49)</p>
  
  <p>What is the problem </p>