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/imap.c

@@ -1176,7 +1176,7 @@ static CURLcode imap_state_login_resp(struct Curl_easy *data,
   return result;
 }
 
-/* Detect IMAP listings vs. downloading a single email  */
+/* Detect IMAP listings vs. downloading a single email */
 static bool is_custom_fetch_listing_match(const char *params)
 {
   /* match " 1:* (FLAGS ..." or " 1,2,3 (FLAGS ..." */
@@ -2324,7 +2324,6 @@ static const struct Curl_protocol Curl_protocol_imap = {
 
 #endif /* CURL_DISABLE_IMAP */
 
-
 /*
  * IMAP protocol handler.
  */