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/libtest/cli_tls_session_reuse.c

@@ -221,7 +221,7 @@ static CURLcode test_cli_tls_session_reuse(const char *URL)
         curl_multi_remove_handle(multi, msg->easy_handle);
         curl_easy_cleanup(msg->easy_handle);
         --ongoing;
-        curl_mfprintf(stderr, "transfer #%" CURL_FORMAT_CURL_OFF_T" retiring "
+        curl_mfprintf(stderr, "transfer #%" CURL_FORMAT_CURL_OFF_T " retiring "
                       "(%d now running)\n", xfer_id, running_handles);
       }
     }