minahito has suggested new rule for the language directory.
(language name)_(encoding) (*) all should be small letters
Of course, this change should be graced for the compatibilities.
French encoded ISO-8859-* should be named "french" as conventional.
French encoded UTF-8 should be named "fr_utf8" newly.
Though my modules contains "japaneseutf" as "Japanese encoded UTF-8",
they should be renamed "ja_utf8" gradually.