- define `SECURITY_WIN32` globally in `curl_setup.h`.
To make sure it applies to all includes.
- document which Windows headers require `SECURITY_WIN32`.
- stop suppressing MSVC warning:
`C4201 is: nonstandard extension used : nameless struct/union`
The warning is no longer seen in supported build envs with the current
codebase.
Follow-up to 8beff43559#8419
- document why `SCHANNEL_USE_BLACKLISTS` is needed.
- just define `SCHANNEL_USE_BLACKLISTS`, drop the unnecessary value `1`.
- stop defining unused `SCH_CRED_MAX_SUPPORTED*` fallback macros.
Follow-up to 8beff43559#8419
- document why `subauth.h` is included (where missing).
- move and de-dupe `subauth.h` include into `curl_setup.h`, limit to
Schannel builds.
- stop include `schnlsp.h`. It is a 1-to-1 compatibility wrapper for
`schannel.h`.
- curl_sspi.h: clarify comment about `SP_NAME_` macros.
They are local macros, their SDK names are different and curl does not
use them.
- curl_sspi.h: drop superfluous includes `security.h` and `rpc.h`.
Cherry-picked from #20556Closes#20564
c220674ac4