I am not hooking these to "make test", for two reasons:
1. utf8_step_forward is inside #ifdef CONFIG_UTF8 and I don't see
how to make tests conditional on such options.
2. test/libtest.sh was copied from Git, which is under GPLv2-only.
Adding more dependencies on it could make ELinks more difficult
to relicense under GPLv2-or-later.
