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-continue>
    <allredirects garcontinue="Clemente_XIII|13186" />
  </query-continue>
  <query>
    <pages>
      <page pageid="7449" ns="0" title="Piotr Celestyn Kaliszewski" />
      <page pageid="7813" ns="0" title="Bernardo Probo" />
      <page pageid="7906" ns="0" title="Carlo Giuseppe De Rossi" />
      <page pageid="7907" ns="0" title="Carlo Giuseppe De Rubeis" />
      <page pageid="8010" ns="0" title="Bernard Syruć" />
      <page pageid="8096" ns="0" title="Baltasar Tonen" />
      <page pageid="13139" ns="0" title="Pietro Francesco Orsini" />
      <page pageid="13141" ns="0" title="Próspero Lorenzo Lambertini" />
      <page pageid="13182" ns="0" title="Julio Rospigliosi" />
      <page pageid="13184" ns="0" title="Ippolito Aldobrandini" />
    </pages>
  </query>
</api>