[meta] Clean up @todos and deprecated code

 * @param $decode
 *   (deprecated) Whether to decode entities in the $string. Set to FALSE if the
 *   $string is in plain text, TRUE otherwise. Defaults to TRUE. This parameter
 *   is deprecated and will be removed in Drupal 8. To process a plain-text URI,
 *   call drupal_strip_dangerous_protocols() or check_url() instead.

 * @todo This function is deprecated, and should be removed wherever possible.

   * Returns the languages the entity is translated to.
   *
   * @todo: Remove once all entity types implement the entity field API. This
   * is deprecated by
   * TranslatableInterface::getTranslationLanguages().

 * @deprecated
 *   This mechanism for registering routes is temporary. It will be replaced
 *   by a more robust mechanism in the near future.  It is documented here
 *   only for completeness.

 * Deprecated. Use %user_uid_optional instead.
 *
 * @todo D8: Remove.

    // @todo D8: Add a drupal_css_defaults() helper function.

   * @todo Update for D8 configuration system.

  // @todo D8: Convert to new state storage.

    // @todo: Fix me in D8: We need a way to set multiple errors on the same
    // form element and have all of them appear!

    // @todo Legacy support. Remove in Drupal 8.
    if (isset($settings['method']) && $settings['method'] == 'replace') {
      $settings['method'] = 'replaceWith';
    }

      // @todo Legacy support. Remove in Drupal 8.
      $form_state['clicked_button'] = $form_state['triggering_element'];

  // Caching is normally done in drupal_process_form(), but what needs to be
  // cached is the $form structure before it passes through form_builder(),
  // so we need to do it here.
  // @todo For Drupal 8, find a way to avoid this code duplication.
  if (empty($form_state['no_cache'])) {
    form_set_cache($form['#build_id'], $form, $form_state);
  }

 *   - #empty_value: (optional) The value for the first default option, which is
 *     used to determine whether the user submitted a value or not.
 *     - If #required is TRUE, this defaults to '' (an empty string).
 *     - If #required is not TRUE and this value isn't set, then no extra option
 *       is added to the select control, leaving the control in a slightly
 *       illogical state, because there's no way for the user to select nothing,
 *       since all user agents automatically preselect the first available
 *       option. But people are used to this being the behavior of select
 *       controls.
 *       @todo Address the above issue in Drupal 8.
 *     - If #required is not TRUE and this value is set (most commonly to an
 *       empty string), then an extra option (see #empty_option above)
 *       representing a "non-selection" is added with this as its value.

      // Integer 0 is not a valid #return_value, so use '0' instead.
      // @see form_type_checkbox_value().
      // @todo For Drupal 8, cast all integer keys to strings for consistency
      //   with form_process_radios().
      if ($key === 0) {
        $key = '0';
      }

  /**
   * Minimum engine version.
   *
   * @todo Consider upping to 3.6.8 in Drupal 8 to get SAVEPOINT support.
   */
  public function minimumVersion() {
    return '3.3.7';
  }

  public function minimumVersion() {
    return '3.7.11';
  }

  // @todo Remove backwards compatibility in Drupal 8, and use a unique
  // $form_state['field'][...$parents...]['#fields'][$field_name] structure.

 * @todo rethink the naming of this in Drupal 8.

 * @todo rethink the naming of this in Drupal 8.

    // @todo This alters and replaces the original object value, so a
    //   hypothetical process of loading, viewing, and saving will hijack the
    //   stored data. Consider renaming to $comment->signature_safe or similar
    //   here and elsewhere in Drupal 8.
    $comment->signature = check_markup($comment->signature, $comment->signature_format, '', TRUE);