Enable it for `_MSC_VER <= 1943`.
Omit it for not yet CI-tested MSVC versions, to avoid hitting unfixed
warnings emitted by future toolchain releases. It means we need
to explicitly opt-in to newer MSVC versions while fixing any new issues.
The newly enabled warnings did not reveal new issues. It hints that we
catch those with clang/gcc. Yet, these warnings may be useful for local
development done with MSVC.
Also:
- disable and document warnings that don't seem useful, unactionable,
or unfixable.
- disable and document warnings found in Windows SDK headers.
- tidy up a few comments, also to avoid
`-Wdocumentation-unknown-command`, part of llvm/clang `-Wall`.
```
lib\dynhds.h(159,29): error : unknown command tag name [-Werror,-Wdocumentation-unknown-command]
lib\ftp.c(337,15): error : unknown command tag name [-Werror,-Wdocumentation-unknown-command]
```
(This patch did not end up enabling `-Wall` for clang-cl.)
Closes#17050
8478365e29