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

lib/rtsp.c

@@ -234,7 +234,7 @@ static CURLcode rtsp_setup_body(struct Curl_easy *data,
       /* As stated in the http comments, it is probably not wise to
        * actually set a custom Content-Length in the headers */
       if(!Curl_checkheaders(data, STRCONST("Content-Length"))) {
-        result = curlx_dyn_addf(reqp, "Content-Length: %" FMT_OFF_T"\r\n",
+        result = curlx_dyn_addf(reqp, "Content-Length: %" FMT_OFF_T "\r\n",
                                 req_clen);
         if(result)
           return result;