title: cleveref fails for theorem environments sharing the same counter
body: <p>I want to number all theorems and corollaries on the same (section) counter.  But when I do this, cleveref names them both 'theorem'.  Here is a minimal example:</p>
  
  <pre><code>\documentclass{amsart}
  
  \usepackage{amsthm, cleveref}
  %\crefname{theorem}{theorem}{theorems}
  %\crefname{corollary}{corollary}{corollaries}
  
  \newtheorem{theorem}{Theorem}[section]
  \newtheorem{corollary}[theorem]{Corollary}
  
  \begin{document}
  \section{Section title}
  
  \begin{theorem}\label{thm:test}
  Here is the theorem.
  \end{theorem}
  
  \begin{corollary}\label{cor:test}
  Here is the corollary.
  \end{corollary}
  
  The theorem reference is given by \cref{thm:test} and the corollary reference is given by \cref{cor:test}.
  
  \end{document}
  </code></pre>
  
  <p>Here, the corollary reference is 'theorem 1.2'.  This problem persists even when explicitly stating the crefname.</p>
  
  <p>Any suggestions?</p>