title: ocamltop like 'trace' directive in ocamldebug
body: <p>Is there a ocamltop's <code>trace</code> directive equivalent in ocamldebug ?</p>
  
  <p>I need to use ocamldebug because my project has a few dozens of files and loading them into ocamltop hard(load order matters etc.). With ocamldebug, I can just give the compiled file and it works.</p>
  
  <p>For now I'm using some custom identity functions to trace function calls in ocamldebug. Ie. I have several identity functions:</p>
  
  <pre><code>let id_some_fun_1 a p1 p2 = a p1 p2
  let id_some_fun_2 a p = a p
  </code></pre>
  
  <p>Then in my code, I'm wrapping the function I want to trace with this functions, and then I'm setting breakpoints.</p>
  
  <p>As you may have guessed, this is way harder than just running <code>#trace some_fun_1</code>.</p>
  
  <p>Thanks in advance.</p>