tidy-up: miscellaneous

- examples: sync debug output printf masks.
- INSTALL-CMAKE.md: tidy up section for some options.
- curl_sha512_256: delete comment suggesting an optimization.
- vtls/keylog: scope a variable.
- vtls/openssl: make a source code URL a permalink.
- vtls/schannel: drop redundant parentheses.
- test1119.pl: robustify `$1` -> `$s`.
- sync arg names in comments to match the code.
- tidy up and minor fixes to comments.
- fix formatting/indenting/comment/newline/include nits.
- move `UNITTEST` protos next to definitions, sync their argument names.
- make variables static.
- add parentheses to Perl `open()` calls.
- drop unnecessary double quotes in Perl.
- clang-format.

Closes #21000

tests/servers.pm

@@ -1899,7 +1899,7 @@ sub runsshserver {
        !close($hostfile) ||
        ($SSHSRVMD5 !~ /^[a-f0-9]{32}$/i))
     {
-        my $msg = "Fatal: $srvrname pubkey md5 missing : \"$hstpubmd5f\" : $!";
+        my $msg = "Fatal: $srvrname pubkey MD5 missing : \"$hstpubmd5f\" : $!";
         logmsg "$msg\n";
         stopservers($verb);
         die $msg;
@@ -1909,7 +1909,7 @@ sub runsshserver {
        (read($hostfile, $SSHSRVSHA256, 48) == 0) ||
        !close($hostfile))
     {
-        my $msg = "Fatal: $srvrname pubkey sha256 missing : \"$hstpubsha256f\" : $!";
+        my $msg = "Fatal: $srvrname pubkey SHA256 missing : \"$hstpubsha256f\" : $!";
         logmsg "$msg\n";
         stopservers($verb);
         die $msg;