Fix visual glitch for long CJK names w/o cropping

It's caused by ncurses and/or terminal emulator, as one of these
two refuses to draw in the middle of a wide-character symbol.

Thanks to anonymous from linux.org.ru.
Add unit-test for CJK long name glitch
Add missing "of" to get_normal_utf8_string_length

Just correct the comment.
Merge branch 'fix-wide-chars-overflow-glitch'

Fix visual glitch for long wide character (CJK) file names with disabled
cropping.

Thanks to anonymous from linux.org.ru.