title: Why isn't there boost::intrusive::map?
body: <p>The boost documentation (<a href="http://www.boost.org/doc/libs/1_55_0/doc/html/intrusive.html" rel="nofollow">http://www.boost.org/doc/libs/1_55_0/doc/html/intrusive.html</a>) states that the intrusive containers are implemented for <code>list</code> (both single/double linked), <code>set</code> and <code>multiset</code>.
  I couldn't find an implementation for the map. Is there any deeper reason for it, or is it just waiting to be implemented?</p>