Search Settings page breaks with "Call to undefined function apachesolr_index_status()"

With a recent update to Solr, the search settings breaks if Apache Solr Attachments is installed.

This is related to a very similar bug in ApacheSolr module itself, #1396606: Fatal error "Call to undefined function apachesolr_index_status()" when visiting admin/config/search/settings, and I've found that the same fix works. We just need to include the apachesolr.index file, so the function apachesolr_index_status() is defined.

Needs this explicit module_load_include() added to apachesolr_attachments_search_status() in apachesolr_attachments.module:

/**
 * Implements hook_search_status().
 *
 * @see apachesolr_search_search_status()
 */
function apachesolr_attachments_search_status() {
  // TODO: Figure out a way to know how many actual files are left to update.
  module_load_include('inc', 'apachesolr', 'apachesolr.index');
  return apachesolr_index_status('apachesolr_attachments');
}