- lib/connect.c: unused since:
  71b7e01 #10141

- lib/curl_sspi.c: unused since:
  0d71b18 #17413

Cherry-picked from #18009
Closes #18011

Seen with a non-unity, mingw-w64 CI job targeting a Vista+ Windows
version while working on a PR. This combination is not normally
tested in CI.

Fixing:
```
In file included from D:/my-cache/mingw32/i686-w64-mingw32/include/iprtrmib.h:9:0,
                 from D:/my-cache/mingw32/i686-w64-mingw32/include/iphlpapi.h:17,
                 from D:/a/curl/curl/lib/url.c:63:
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:865:3: error: unknown type name 'CERT_NAME_BLOB'
   CERT_NAME_BLOB *certificateNames;
   ^~~~~~~~~~~~~~
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:887:3: error: unknown type name 'CRYPT_HASH_BLOB'
   CRYPT_HASH_BLOB certBlob;
   ^~~~~~~~~~~~~~~
```
Ref: https://github.com/curl/curl/actions/runs/16497057672/job/46645264552?pr=18012#step:10:140

Follow-up to 0d71b18 curl#17413
Ref: curl#18009

Seen with a non-unity, mingw-w64 CI job targeting a Vista+ Windows
version while working on a PR. This combination is not normally
tested in CI.

Fixing:
```
In file included from D:/my-cache/mingw32/i686-w64-mingw32/include/iprtrmib.h:9:0,
                 from D:/my-cache/mingw32/i686-w64-mingw32/include/iphlpapi.h:17,
                 from D:/a/curl/curl/lib/url.c:63:
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:865:3: error: unknown type name 'CERT_NAME_BLOB'
   CERT_NAME_BLOB *certificateNames;
   ^~~~~~~~~~~~~~
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:887:3: error: unknown type name 'CRYPT_HASH_BLOB'
   CRYPT_HASH_BLOB certBlob;
   ^~~~~~~~~~~~~~~
```
Ref: https://github.com/curl/curl/actions/runs/16497057672/job/46645264552?pr=18012#step:10:140

Follow-up to 0d71b18 curl#17413
Ref: curl#18009

Required for mingw-w64 5.x (and older) builds targeting a Windows 7+.

mingw-w64 6+ fixed `mprapi.h` (included indirectly via `iphlpapi.h`)
to include `wincrypt.h` for the missing types.

MSVC is not affected because SDK 7.1a (the oldest MS SDK curl supports),
`mprapi.h` does include `wincrypt.h`.

Make sure to include `wincrypt.h` before including `iphlpapi.h` as
a workaround. `wincrypt.h` is used unconditionally even though it's
not available in UWP. This is safe in this context, because we use
`iphlpapi.h` for `if_nametoindex`, which is not supported and used
in UWP builds.

This fixes auto-detection that missed detecting `if_nametoindex` in
the affected combination, and this build error in non-unity builds:
```
In file included from D:/my-cache/mingw32/i686-w64-mingw32/include/iprtrmib.h:9:0,
                 from D:/my-cache/mingw32/i686-w64-mingw32/include/iphlpapi.h:17,
                 from D:/a/curl/curl/lib/url.c:63:
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:865:3: error: unknown type name 'CERT_NAME_BLOB'
   CERT_NAME_BLOB *certificateNames;
   ^~~~~~~~~~~~~~
D:/my-cache/mingw32/i686-w64-mingw32/include/mprapi.h:887:3: error: unknown type name 'CRYPT_HASH_BLOB'
   CRYPT_HASH_BLOB certBlob;
   ^~~~~~~~~~~~~~~
```
Ref: https://github.com/curl/curl/actions/runs/16497057672/job/46645264552?pr=18012#step:10:140

This combination is not normally tested in CI. It was caught in
the `dl-mingw, CM 6.4.0-i686 schannel !unity Win7` job while working
on another PR.

Follow-up to 0d71b18 #17413
Ref: #18009
Closes #18012

Collision happens when building with mingw-w64 v3 or v2 while targeting
Vista or newer. `iphlpapi.h` includes `windns.h` in this case, which
defines macros named `DNS_TYPE_*`, colliding with curl doh enums.

The issue was fixed in mingw-w64 v4:
mirror/mingw-w64@ea95d55

Fixes:
```
lib/doh.h:54:3: error: expected identifier before numeric constant
   DNS_TYPE_A = 1,
   ^
```
Ref: https://github.com/curl/curl/actions/runs/16551209676/job/46806303365?pr=18009#step:10:17

This workaround seems harmless and generally good practice, but
another option is to require mingw-w64 v4.

Ref: #18009
Closes #18041