- Fix mistake reported here:

    http://root.cern.ch/phpBB3/viewtopic.php?f=10&t=13771
- Make sure the code examples do no start with a blank line
- Remove the useless <code></code> in <programlisting>
- Make sure the listings do not exit the grey boxes


git-svn-id: http://root.cern.ch/svn/root/trunk@42326 27541ba8-7e3a-0410-8455-c3a389f83636