Problem:    Small source file problems; outdated list of distributed files.
Solution:   Small updates to source files and list of distributed files.

Problem:    CI does not run sound tests.
Solution:   Re-enable sound tests.  Use "apt-get" instead of "apt". (Ozaki
            Kiichi, closes #12280)

Problem:    Testing with Python on AppVeyor does not work properly.
Solution:   Fix typo.  Move most lines to the .bat file. (Christopher
            Plewright, closes #11828)

Problem:    AppVeyor builds with an old Python version.
Solution:   Switch from Python 3.8 to 3.11. (Christopher Plewright,
            closes #11814)

Problem:    AppVeyor runs much slower with MSVC 2022.
Solution:   Go back to MSVC 2015. (Christopher Plewright, closes #11810)

Problem:    AppVeyor uses some older tools.
Solution:   Switch to Visual Studio 2022 and Python 3.11. (Christopher
            Plewright, closes #11793)

Problem:    MS-Windows: clumsy way to suppress progress on CI.
Solution:   Check for "$CI" in the Makefile itself. (Ken Takata, closes #9631)

Problem:    Cannot build with dynamic Ruby 3.1.
Solution:   Add "_EXTRA" variables for CI.  Add missing functions. (Ozaki
            Kiichi, closes #9420)

Problem:    New compiler warnings from clang-12 and clang-13.
Solution:   Adjust CI and suppress some warnings. (Ozaki Kiichi, closes #9314)

Problem:    Appveyor script does not detect nmake failure.
Solution:   Explicitly check for executable. (Ken Takata, closes #8281)