Lesser form of include-what-you-use: at least guarantees that header
file did not forget to include something through some other included
file.

Activate run_single_includes_tests on CI.
Fix some IWYU violations.

References #5321

Problem:    Man test fails when run with the GUI.
Solution:   Adjust for different behavior of GUI.  Add assert_inrange().

https://github.com/vim/vim/commit/61c04493b00f85d0b97436260a9ef9ab82143b78

Only changes related to assert_inrange() were included, since we have a
distinct man plugin.

If I am not mistaking, this commit should not change any functionality.

Problem:    Double free on exit when using a closure. (James McCoy)
Solution:   Split free_al_functions in two parts. (closes #1428)

https://github.com/vim/vim/commit/03ff9bcbc968f7d306e4a4e334e226fdde62ca82

Problem:    Leaking memory when redefining a function.
Solution:   Don't increment the function reference count when it's found by
            name. Don't remove the wrong function from the hashtab.  More
            reference counting fixes.

https://github.com/vim/vim/commit/8dd3a43d75550e9b5736066124c97697564f769e

Problem:    Using function() with a name will find another function when it is
            redefined.
Solution:   Add funcref().  Refer to lambda using a partial.  Fix several
            reference counting issues.

https://github.com/vim/vim/commit/437bafe4c8a83ed71ee006eda7f54b65a90f0d4c

Problem:    Using submatch() in a lambda passed to substitute() is verbose.
Solution:   Use a static list and pass it as an optional argument to the
            function.  Fix memory leak.

https://github.com/vim/vim/commit/df48fb456fb6bf63d94cad9b302ff01d8ee8d311