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>
    <alltransclusions gatcontinue="Nota|149" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Página principal" />
      <page pageid="6" ns="0" title="Instalação do DSpace 3.1" />
      <page pageid="11" ns="0" title="Upgrade de versões" />
      <page pageid="15" ns="0" title="Formulário de entrada" />
      <page pageid="27" ns="0" title="Instalação da versão 2.05" />
      <page pageid="66" ns="0" title="Embargo na interface JSPUI" />
      <page pageid="70" ns="0" title="Instalação do DSpace 3.x" />
      <page pageid="97" ns="0" title="Oai" />
      <page pageid="133" ns="0" title="Configurações de idioma" />
      <page pageid="141" ns="0" title="Instalação SEER 2.x" />
    </pages>
  </query>
</api>