Problem:    Parallel make might not work.
Solution:   Add missing dependencies. (Samuel Dionne-Riel, closes #12288)

Problem:    Classes are not documented or implemented yet.
Solution:   Make the first steps at documenting Vim9 objects, classes and
            interfaces.  Make initial choices for the syntax.  Add a skeleton
            implementation.  Add "public" and "this" in the command table.

Problem:    It is not easy to see what client-server commands are doing.
Solution:   Add channel log messages if ch_log() is available.  Move the
            channel logging and make it available with the +eval feature.

Problem:    Various comment and indent flaws.
Solution:   Improve comments and indenting.

Problem:    There is no real need for a "big" build.
Solution:   Move common features to "normal" build, less often used features
            to the "huge" build. (Martin Tournoij, closes #11283)

Problem:    Too many #ifdefs.
Solution:   Graduate the +cmdwin feature.  Now the tiny and small builds are
            equal, drop the small build.  (Martin Tournoij, closes #11268)

Problem:    Makefile error message causes a shell error.
Solution:   Put the message in single quotes. (closes #11232)

Problem:    Missing dependency may cause crashes on incomplete build.
Solution:   Add dependency.