tidy-up: miscellaneous

- vms/curlmsg_vms.h: delete unused/commented code.
- vtls/schannel_verify: sort includes.
- typecheck-gcc.h: fix indent and alignment.
- lib/config-win32.h: drop idle `#undef`.
- spacecheck: check for stray empty lines before after curly braces.
- make literals more readable: 1048576 -> 1024 * 1024
- scope variables.
- use ISO date in a comment.
- drop redundant parentheses.
- drop empty comments.
- unfold lines.
- duplicate/stray spaces in comments.
- fix indent, whitespace, minor typos.

Closes #20690

lib/smtp.c

@@ -1061,9 +1061,9 @@ static CURLcode smtp_perform_mail(struct Curl_easy *data,
                          "MAIL FROM:%s%s%s%s%s%s",
                          from,                 /* Mandatory                 */
                          auth ? " AUTH=" : "", /* Optional on AUTH support  */
-                         auth ? auth : "",     /*                           */
+                         auth ? auth : "",
                          size ? " SIZE=" : "", /* Optional on SIZE support  */
-                         size ? size : "",     /*                           */
+                         size ? size : "",
                          utf8 ? " SMTPUTF8"    /* Internationalised mailbox */
                                : "");          /* included in our envelope  */