For `GetLastError()` and `SECURITY_STATUS`:
0x-prefixed, 8-digit, lowercase, hex: 0x1234abcd
Also: say `GetLastError()` instead of `errno` in one message.
Closes#18877
- curlx_get_winapi_error: accept DWORD (was: int), move casts one level
up the callstack.
- sspi: bump some types to `SECURITY_STATUS` (int -> LONG).
- digest_sspi: drop unnecessary cast.
Closes#18868
Also:
- tests/server: replace local `sstrerror()` with `curlx_strerror()`.
- tests/server: show the error code next to the string, where missing.
- curlx: use `curl_msnprintf()` when building for src and tests.
(units was already using it.)
- lib: drop unused includes found along the way.
- curlx_strerror(): avoid compiler warning (and another similar one):
```
In file included from servers.c:14:
../../lib/../../lib/curlx/strerr.c: In function ‘curlx_strerror’:
../../lib/../../lib/curlx/strerr.c:328:32: error: ‘snprintf’ output may be truncated before the last format character [-Werror=format-truncation=]
328 | SNPRINTF(buf, buflen, "%s", msg);
| ^
../../lib/../../lib/curlx/strerr.c:47:18: note: ‘snprintf’ output 1 or more bytes (assuming 2) into a destination of size 1
47 | #define SNPRINTF snprintf
| ^
../../lib/../../lib/curlx/strerr.c:328:7: note: in expansion of macro ‘SNPRINTF’
328 | SNPRINTF(buf, buflen, "%s", msg);
| ^~~~~~~~
```
Follow-up to 45438c8d6f#18823Closes#18840
Drop the interim macro `PRESERVE_WINDOWS_ERROR_CODE` and always preserve
error code for `_WIN32`. To make sure this is always done in
`curlx_winapi_strerror()`.
Follow-up to c74d3e10d2#17299Closes#17302
