Document D6 use of custom_url_rewrite_outbound()

Drupal 6.2 + Domain Access 6.x-1.0-beta2 + domain configuration + domain content + domain navigation + domain source + domain theme

If i get it right, this function is in D6core. And we do not need a patch for using it.
And after installing i get :

"The custom_url_rewrite_outbound() function is not installed. Some features are not available. See the custom_url_rewrite_outbound() section of INSTALL.txt"

and i cant switch to "Search all domains from any URL" or "Rewrite all URLs to point to a single source"

All the information about this patch is deleted from readme.txt, install.txt.

I add this lines from install.txt from domain-5.x-1.0 and it helped to fix the issue:

/**
 * Add the custom_url_rewrite_outbound function.
 */
require_once './sites/all/modules/domain/settings_custom_url.inc'; 

If this is the right way, then it should be documented.