You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <allredirects>
      <r fromid="398" ns="0" title="ClamAV" />
      <r fromid="482" ns="0" title="Commandes reseaux Linux" />
      <r fromid="309" ns="0" title="Configurer reseau Windows" />
      <r fromid="345" ns="0" title="Debug Messagerie" />
      <r fromid="334" ns="0" title="Routage IPv6" />
      <r fromid="292" ns="0" title="Routage statique IPv6" />
      <r fromid="343" ns="0" title="Serveur DNS" />
      <r fromid="402" ns="0" title="SpamAssassin" />
    </allredirects>
  </query>
</api>