Switch encodings of tutorials, thai-word to UTF-8.

Switch encodings of tutorials, thai-word to UTF-8.

* etc/refcards/ru-refcard.tex:
* etc/tutorials/TUTORIAL.bg, etc/tutorials/TUTORIAL.bg, etc/tutorials/TUTORIAL.cn:
* etc/tutorials/TUTORIAL.cs, etc/tutorials/TUTORIAL.de, etc/tutorials/TUTORIAL.eo:
* etc/tutorials/TUTORIAL.es, etc/tutorials/TUTORIAL.fr, etc/tutorials/TUTORIAL.it:
* etc/tutorials/TUTORIAL.nl, etc/tutorials/TUTORIAL.pl, etc/tutorials/TUTORIAL.pt_BR:
* etc/tutorials/TUTORIAL.ro, etc/tutorials/TUTORIAL.sk, etc/tutorials/TUTORIAL.sv:
* etc/tutorials/TUTORIAL.zh:
* lisp/language/thai-word.el:
Switch to UTF-8.

Fixes: debbugs:13880