Apache Solr language filter

Filter the apachesolr result to language neutral or active language only.

bug: the language filter is displayed in the breadcrumb, and there is no way in apachesolr-6.x-1.x to remove this filter form the breadcrumb..
workaround: add this code into _preprecess_page(&$vars)

  if (arg(0) == 'search') {
    // Remove language filters from breadcrumb. This could be removed when
    // apachesolr-6.x-2.x will be used on the site.
    $breadcrumb = drupal_get_breadcrumb();
    $langcodes = array_keys(language_list());
    foreach ($breadcrumb as $key => $link) {
      if (strpos($link, '-language') || in_array($link, $langcodes)) {
        unset($breadcrumb[$key]);
      }
    }
    // The last breadcrumb is the current page, so it shouldn't be a link.
    $last = count($breadcrumb) - 1;
    $breadcrumb[$last] = strip_tags($breadcrumb[$last]);
    $vars['breadcrumb'] = theme('breadcrumb', $breadcrumb);
  }