Problem:    Display wrong when moving cursor to above the top line and
            'smoothscroll' is set.
Solution:   Call adjust_skipcol() in more places and make it work better.
            (Luuk van Baal, closes #12395)

Problem:    Display errors when making topline shorter and 'smoothscroll' is
            set.
Solution:   Reset w_skipcol when the topline becomes shorter than its current
            value. (Luuk van Baal, closes #12367)

Problem:    Line not fully displayed if it doesn't fit in the screen.
Solution:   Do not reset s_skipcol if not needed. (Luuk van Baal,
            closes #12376)

Problem:    No test for deleting the end of a long wrapped line.
Solution:   Add a test to check the right text is displayed. (Luuk van Baal,
            closes #12318)

Problem:    Matchparen highlight is not updated when switching buffers.
Solution:   Listen to the BufLeave and the BufWinEnter autocmd events.
            (closes #11626)

Problem:    Display test for 'listchars' "precedes" fails.
Solution:   Correct the expected result.

Problem:    Multi-byte "lastline" item in 'fillchars' does not work properly
            when the window is two columns wide.
Solution:   Compute the text length correctly. (closes #11280)

Problem:    Cannot specify another character to use instead of '@' at the end
            of the window.
Solution:   Add "lastline" to 'fillchars'. (Martin Tournoij, closes #11264,
            closes #10963)

Problem:    Some tests are failing.
Solution:   Adjust for "<<<" showing up.

Problem:    Manually deleting temp test files.
Solution:   Add the 'D' flag to writefile().