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

scripts/cd2cd

@@ -69,7 +69,7 @@ sub outseealso {
     my @o;
     push @o, ".SH SEE ALSO\n";
     for my $s (sort @sa) {
-        push @o, sprintf "%s.BR $s", $comma ? ",\n": "";
+        push @o, sprintf "%s.BR $s", $comma ? ",\n" : "";
         $comma = 1;
     }
     push @o, "\n";