tidy-up: miscellaneous

- gnutls, mbedtls: fix casing in log messages.
- src/tool_cfgable.h: drop unused header.
- appveyor.sh: variable style.
- cmakelint.sh: sync with libssh2, catch `.cmake.in` explicitly.
- examples: drop obsolete comments, exclamation marks.
- fix comment typos, casing.

Closes #19839

docs/examples/anyauthput.c

@@ -150,7 +150,7 @@ int main(int argc, char **argv)
 
     /* tell libcurl we can use "any" auth, which lets the lib pick one, but it
        also costs one extra round-trip and possibly sending of all the PUT
-       data twice!!! */
+       data twice */
     curl_easy_setopt(curl, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
 
     /* set username and password for the authentication */