title: Display current line and column number for a textarea
body: <p>I'm making a file edit interface in my web-app, I have a textarea with file contents.</p>
  
  <p>When textarea is focused, I want to output the position of the cursor, i.e. line number and column: this is useful because error messages usually yield a line number, for example.</p>
  
  <p>The question is: how do I figure out the position of the cursor in textarea?
  I'm using prototype library. Maybe there's a solution already?</p>
  
  <p>I'm not really interested in fancy toolbars for the textarea, which are offered by those advanced widgets.</p>