[WIP] build: enable WinIDN by default

[vszakats]

Windows XP is not compatible with WinIDN by default. It requires
a Normaliz.dll to be installed, but the necessary package is no longer
offered by Microsoft. Thus, for Windows XP compatibility, we recommend
building with -DUSE_WIN32_IDN=OFF.

Discussion: #13565
Closes #13947

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Cleaner diff without whitespace changes: https://github.com/curl/curl/pull/13947/files?w=1

There are a few ways to resolve compatibility with existing builds
and also to handle interactions with the USE_LIBIDN2 option.
This is an initial attempt.

TODO:

• cmake: detect WinXP target using HAVE_WIN32_WINNT and adjust default USE_WIN32_IDN setting accordingly?
• review and update CI jobs where/if necessary.
• review and fixup WinIDN / libidn2 interactions in autotools.
• fix autotools logic to only make WinIDN the default when targeting native Windows.
• figure out how to make IDN tests work on Windows.
• split off VS2008 log dump on failure in AppVeyor into separate PR. → appveyor: dump build logs on failure in VS2008 jobs #13957

[vszakats]

Tests are unprepared to handle IDN with Windows, both UNICODE and non-UNICODE modes (but differently).

[vszakats]

Unexpected fallout with VS2008. Vista target, Normaliz.lib specified, yet the IDN functions are not found:

6>unity_0.obj : error LNK2019: unresolved external symbol __imp__IdnToAscii@20 referenced in function _win32_idn_to_ascii
6>unity_0.obj : error LNK2019: unresolved external symbol __imp__IdnToUnicode@20 referenced in function _win32_ascii_to_idn
6>C:\projects\curl\_bld\lib\libcurl.dll : fatal error LNK1120: 2 unresolved externals

Anybody with a solution for the above issue?

I still couldn't figure out how to enable verbose logging for the VS2008 jobs. [RESOLVED]

[vszakats]

The VS2008 issue was reported here earlier: #1863

This trace message says that normaliz is added to the list of libs:

-- ws2_32;bcrypt;wldap32;normaliz

Ref: https://ci.appveyor.com/project/curlorg/curl/builds/50021801/job/xpd1d5cor294gp3m#L42

It feels like something very obvious (or something very cryptic). Seeing the actual linker command would tell more of what's happening.

[vszakats]

Backing off of this. It looks nearly hopeless to make IDN tests pass on Windows (without going crazies that is.) It needs passing Unicode text via the command-line for starters. Also the unexplained VC2008 fallout. Then autotools.

I might cherry pick the part moving WINVER detection up to the top.

Feel free to pick up and continue.