Problem:    Various code not covered by tests.
Solution:   Add a few more test. (Yegappan Lakshmanan, closes #7995)

Problem:    FocusGained does not work when 'ttymouse' is empty.
Solution:   Don't use the short mouse code if there is a longer matching code.
            (closes #7755)  Add a test.

Problem:    No way to check for the cmdwin feature, cmdline_hist is now always
            enabled.
Solution:   Add has('cmdwin') support. Skip arglist test on Windows
            temporarily.

Problem:    Termcodes test is flaky when used over ssh with X forwarding.
Solution:   Set 'mousetime' to a larger value. (Dominique Pellé, closes #7576,
            closes #7563)

Problem:    CTRL-V U doesn't work to enter a Unicode character when
            modifyOtherKeys is effective. (Ken Takata)
Solution:   Add a flag to get_literal() for the shift key. (closes #7413)

Problem:    Vim9: E1030 error when using empty string for term_sendkeys().
Solution:   Don't check for an invalid type unless the terminal can't be
            found. (closes #7382)

Problem:    Wrong input if removing shift results in special key code.
Solution:   Handle special key codes. (closes #7189)

Problem:    Mapping Ctrl-key does not work for '{', '}' and '|'.
Solution:   Remove the shift modifier. (closes #6457)

Problem:    Mapping some keys with Ctrl does not work properly.
Solution:   For terminal, GTK and Motif handle "@", "^" and "_" codes.

Problem:    GTK GUI: cannot map alt-? with <A-?>. (Ingo Karkat)
Solution:   Adjust the characters for which the shift modifier is removed.
            (closes #7016)  Make Motif and Win32 use the same function as GTK.