title: Get function's title from documentation
body: <p>I would like to get the title of a base function (e.g.: <code>rnorm</code>) in one of my scripts. That is included in the documentation, but I have no idea how to "grab" it.</p>
  
  <p>I mean the line given in the <em>RD</em> files as <code>\title{}</code> or the top line in documentation.</p>
  
  <p>Is there any simple way to do this <strong>without</strong> calling <code>Rd_db</code> function from <code>tools</code> and parse all RD files -- as having a very big overhead for this simple stuff? Other thing: I tried with <code>parse_Rd</code> too, but:</p>
  
  <ul>
  <li>I do not know which <em>Rd</em> file holds my function,</li>
  <li>I have no <em>Rd</em> files on my system (just <em>rdb</em>, <em>rdx</em> and <em>rds</em>).</li>
  </ul>
  
  <p>So a function to parse the (offline) documentation would be the best :)</p>
  
  <hr>
  
  <p>POC demo:</p>
  
  <pre><code>&gt; get.title("rnorm")
  [1] "The Normal Distribution"
  </code></pre>