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>
    <allfileusages gafcontinue="Halle_Bemassung_OG.pdf" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1019" ns="6" title="File:C-logo claim blacc.png" />
      <page pageid="1020" ns="6" title="File:C-logo claim blue.png" />
      <page pageid="1021" ns="6" title="File:C-logo claim white.png" />
      <page pageid="1007" ns="6" title="File:Club Bemassung.pdf" />
      <page pageid="1009" ns="6" title="File:Club Reihe.pdf" />
      <page pageid="1010" ns="6" title="File:ColumbiaClub Speks deutsch.pdf" />
      <page pageid="1040" ns="6" title="File:Cven 01.jpg" />
      <page pageid="1011" ns="6" title="File:Deutsche Specs 2004.pdf" />
      <page pageid="1012" ns="6" title="File:Grundriss Rigging EG Ger.pdf" />
      <page pageid="1013" ns="6" title="File:Halle Bemassung EG.pdf" />
    </pages>
  </query>
</api>