Allow token types to 'extend' other token types

Think I've actually got this. I thought I'd have to do a whole bunch of token type dependency parsing and graphing, but I don't think that it's likely we'll have a two-deep token type dependency. If so, I have some code ready for that.

Sweet!!! Committing #2 to CVS!
http://drupal.org/cvs?commit=466256

The example we provide is we want [current-user:ip-address] to return the IP address of the current logged-in user, but [user:ip-address] should not be provided as we have no idea what a single user's IP address is.

If ever this needs to resolve two levels of token type dependencies, here's the code I had started writing:

function _token_build_type_dependencies($token_types) {
  $graph = array();
  require_once DRUPAL_ROOT . '/includes/graph.inc';
  foreach ($token_types as $token_type => $token_type_info) {
    $graph[$token_type]['edges'] = array();
    if (isset($token_type_info['type']) && $token_type_info['type'] != $token_type) {
      $graph[$token_type]['edges'][$token_type_info['type']] = 1;
    }
  }
  drupal_depth_first_search($graph);
  foreach ($graph as $token_type => $data) {
    $token_types[$token_type]['weight'] = $data['weight'];
  }
  return $token_types;
}

      $dependent_token_types = _token_build_type_dependencies($token_info['types']);
      uasort($dependent_token_types, 'drupal_sort_weight');
      $dependent_token_types = array_reverse($dependent_token_types, TRUE);