How to translate files, placed in Drupal's 'include' directory?

I need to load translation for all files inside "include" directory during Drupal installation

It's no problem to do that for modules, I just need to create 'translations' directory inside each of the modules and place "language_code.po" into this directory.

I've tried the same开发者_如何学C for "includes" and had no luck.

Most drupal core has been translated. You will need to download the proper language pack in order to use those languages.

Take a look at http://drupal.org/handbook/modules/locale and http://drupal.org/node/21145