Support callback arguments for hook_webform_select_options_info

I recently had need to dynamically create "Pre-Built Option Lists" using hook_webform_select_options_info(). I am integrating Salesforce with the sf_webform module and I wanted to use the picklist values defined in a Salesforce field as the options for a webform select component. Since all of the Salesforce picklist fields have similar array structures in PHP, there is only a single callback function to generate the different option lists -- each call just needs to have different data to work with. However, the callback functionality for select options does not support callback arguments, so there was no straightforward way to get to the data needed in the callback.

I've attached a simple patch which allows you to specify "callback arguments" when defining the option lists in hook_webform_select_options_info().

Sample usage:

function hook_webform_select_options_info() {
  $items = array();

  $items['days'] = array(
    'title' => t('Days of the week'),
    'options callback' => 'webform_options_days',
    'callback arguments' => array("show_weekends" => FALSE),
  );

  return $items;
}

function webform_options_days($component, $flat, $filter, $custom_args) {
    // $custom_args is array("show_weekends" => FALSE)
}