hm snik i think you might have some settings wrong with your pc. samp can support any type of text but only if your system locale setting is correct. i created my own Lithuanian.txt by going in language settings -> administrative -> language for non-unicode programs and setting it to Lithuanian (Lithuania).
then, after a restart, i was able to save text files with special characters without having to save as unicode and without an error coming up. then i joined samp and here it is: