Problem: Various inconsistencies in test files.
Solution: Add modelines where they were missing. Use Check commands instead
of silently skipping over tests. Adjust indents and comments.
(Ken Takata, closes#6695)
Problem: Multibyte characters in 'listchars' don't work correctly if
'linebreak' is also enabled. (Martin Tournoij)
Solution: Make it work correctly. (Christian Brabandt, closes#4822,
closes#4812)
Problem: "extends" from 'listchars' is used when 'list' is off. (Hiroyuki
Yoshinaga)
Solution: Only use the "extends" character when 'list' is on. (Hirohito
Higashi, closes#4360)
Problem: Composing chars on space wrong when 'listchars' is set.
Solution: Do not use "space" and "nbsp" entries of 'listchars' when there is
a composing character. (Yee Cheng Chin, closes#4197)
Problem: When 'listchars' is set a composing char on a space is wrong.
Solution: Separate handling a non-breaking space and a space. (Yasuhiro
Matsumoto, closes#4046)
Problem: Showing two characters for tab is limited.
Solution: Allow for a third character for "tab:" in 'listchars'. (Nathaniel
Braun, Ken Takata, closes#3810)
