@pigos. Thanks for posting. I removed that feature in the current version because I had complaints about multilingual sites not being able to show the translated text. So, filetext, sizetext and datetext are not applicable any more. I document this in the CHANGELOG.php file.
To get localized (language-specific) headings, just create a language INI file for your specific language, and add the relevant key. You can look at one of the existing INI files to do this. After you create the two file, you upload the two INI files into administrator/language/xx-XX/. Where xx-XX is the language. So, if it is dutch, you would use nl-NL. If it is tialian, you used it-IT.