Gabor, very nice work, thanks!
I found two little bugs, created patches and issued them:
1) When displaying module page for the first time, there is no $_SESSION['autolocale_modules'] yet.
2) Due to one security bug in PHP two years ago, glob() is disabled on many shared hosts. Therefore i suggest to use opendir(), search for files and save them to $files array.
I have also added one more is_readable() check to the code and added drupal_set_message(t('Imported translation file ' . basename($filepath)), 'status'); (Because user need to know something happened to his translations.
Jakub