title: Problem with namespace and libxml when i use Xpath
body: <p>i've got a problem when i'm using libxml with XPath. I want to parse an youtube playlist :</p>
  
  <pre><code>&lt;?xml version='1.0' encoding='UTF-8'?&gt;
  &lt;feed xmlns='http://www.w3.org/2005/Atom'
    xmlns:openSearch='http://a9.com/-/spec/opensearch/1.1/'
    xmlns:media='http://search.yahoo.com/mrss/'
    xmlns:batch='http://schemas.google.com/gdata/batch'
    xmlns:yt='http://gdata.youtube.com/schemas/2007'
    xmlns:gd='http://schemas.google.com/g/2005'
    gd:etag='W/&amp;quot;Dk8DRn47eCp7ImA9WxRQGEk.&amp;quot;'&gt;
    &lt;id&gt;tag:youtube,2008:user:andyland74:playlists&lt;/id&gt;
    &lt;updated&gt;2008-07-21T16:43:25.232Z&lt;/updated&gt;
    &lt;category scheme='http://schemas.google.com/g/2005#kind'
      term='http://gdata.youtube.com/schemas/2007#playlistLink'/&gt;
    &lt;title&gt;Playlists of andyland74&lt;/title&gt;
    &lt;logo&gt;http://www.youtube.com/img/pic_youtubelogo_123x63.gif&lt;/logo&gt;
    &lt;link rel='related' type='application/atom+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74?v=2'/&gt;
    &lt;link rel='alternate' type='text/html'
      href='http://www.youtube.com/profile_play_list?user=andyland74'/&gt;
    &lt;link rel='http://schemas.google.com/g/2005#feed'
      type='application/atom+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists?v=2'/&gt;
    &lt;link rel='http://schemas.google.com/g/2005#post'
      type='application/atom+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists?v=2'/&gt;
    &lt;link rel='http://schemas.google.com/g/2005#batch'
      type='application/atom+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists/batch?v=2'/&gt;
    &lt;link rel='self' type='application/atom+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists?...'/&gt;
    &lt;link rel='service' type='application/atomsvc+xml'
      href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists?alt=...'/&gt;
    &lt;author&gt;
      &lt;name&gt;andyland74&lt;/name&gt;
      &lt;uri&gt;http://gdata.youtube.com/feeds/api/users/andyland74&lt;/uri&gt;
    &lt;/author&gt;
    &lt;generator version='2.0'
      uri='http://gdata.youtube.com/'&gt;YouTube data API&lt;/generator&gt;
    &lt;openSearch:totalResults&gt;3&lt;/openSearch:totalResults&gt;
    &lt;openSearch:startIndex&gt;1&lt;/openSearch:startIndex&gt;
    &lt;openSearch:itemsPerPage&gt;25&lt;/openSearch:itemsPerPage&gt;
    &lt;entry gd:etag='W/&amp;quot;Dk8DRn47eCp7ImA9WxRQGEk.&amp;quot;'&gt;
      &lt;id&gt;tag:youtube,2008:user:andyland74:playlist:8BCDD04DE8F771B2&lt;/id&gt;
      &lt;published&gt;2007-11-04T17:30:27.000-08:00&lt;/published&gt;
      &lt;updated&gt;2008-07-15T12:33:20.000-07:00&lt;/updated&gt;
      &lt;app:edited xmlns:app='http://www.w3.org/2007/app'&gt;2008-07-15T12:33:20.000-07:00&lt;/app:edited&gt;
      &lt;category scheme='http://schemas.google.com/g/2005#kind'
        term='http://gdata.youtube.com/schemas/2007#playlistLink'/&gt;
      &lt;title&gt;My New Playlist Title&lt;/title&gt;
      &lt;summary&gt;My new playlist Description&lt;/summary&gt;
      &lt;content type='application/atom+xml;type=feed'
        src='http://gdata.youtube.com/feeds/api/playlists/8BCDD04DE8F771B2?v=2'/&gt;
      &lt;link rel='related' type='application/atom+xml'
        href='http://gdata.youtube.com/feeds/api/users/andyland74?v=2'/&gt;
      &lt;link rel='alternate' type='text/html'
        href='http://www.youtube.com/view_play_list?p=8BCDD04DE8F771B2'/&gt;
      &lt;link rel='self' type='application/atom+xml'
        href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists/8BCDD04DE8F771B2?v=2'/&gt;
      &lt;link rel='edit' type='application/atom+xml'
        href='http://gdata.youtube.com/feeds/api/users/andyland74/playlists/8BCDD04DE8F771B2?v=2'/&gt;
      &lt;author&gt;
        &lt;name&gt;andyland74&lt;/name&gt;
        &lt;uri&gt;http://gdata.youtube.com/feeds/api/users/andyland74&lt;/uri&gt;
      &lt;/author&gt;
      &lt;yt:countHint&gt;9&lt;/yt:countHint&gt;
    &lt;/entry&gt;
  &lt;/feed&gt;
  </code></pre>
  
  <p>when i use the following xpath expression "/feed", the xmlXPathEvalExpression say me that i doesnt find.</p>
  
  <p>if i remove all the xmlns attributes of feed it works. How could i make it work even with xmlns attributes ?</p>
  
  <p>i use libxml with objective-C  </p>