tidy-up: miscellaneous

- curl_ntlm_core, smtp, schannel: fix comments.
- curl_setup.h: fix to undef before define.
- tool_doswin, server/sockfilt: reduce variables scopes.
- tool_doswin: drop an interim variable.
- windows: replace `SOCKET_ERROR` with `0` to align with rest of code.
- libssh2: rename variable to align with rest of code.
- gtls, unit1398: use `#if 0`.
- curl_trc.h, curlx/inet_ntop.h: add missing parentheses in macro
  expressions.
- ldap.c: set empty macro to `do {} while(0)`.
- examples/crawler: rename a non-CURLcode `result` variable.
- CURLINFO_TLS_SESSION: drop stray colon.
- add `const` to casts where missing.
- drop unnecessary parentheses.
- fix indent.
- quote style.
- comment style.
- whitespace, newlines, fold/unfold.

Closes #20554

lib/http.c

@@ -4062,7 +4062,7 @@ static CURLcode http_on_response(struct Curl_easy *data,
     goto out;
 
   if(k->httpcode >= 300) {
-    if((!data->req.authneg) && !conn->bits.close &&
+    if(!data->req.authneg && !conn->bits.close &&
        !Curl_creader_will_rewind(data)) {
       /*
        * General treatment of errors when about to send data. Including :