Upgrade the Drupal 6 core patch to match the committed Drupal 7 core patch

The CDN integration module uses the custom_file_url_rewrite function. But the Drupal core patch uses a hook: hook_file_url_alter(). Initially, they agreed with the special function approach, as the same approach is used for rewriting URLs. But now they're shifting all of the URL rewriting functions (including file URL rewriting) to using hooks, to prevent confusing developers with this special case, and because then you can have a module implementing it, instead of having to add some special code.

So the Drupal 6 patch included in this module should be updated to use the same approach.