tidy-up: URLs (cont.) and mdlinkcheck

- add missing ending slashes.
  To avoid duplicates and to use canonical URLs.
- reapply lost updates.
  Follow-up to 2ae983bf4e #19879
- mdlinkcheck: include the `include` directory.
- mdlinkcheck: show unused whitelist items.
- mdlinkcheck: improve debug output.
- mdlinkcheck: delete redundant whitelist items.
- examples/simplessl: lowercase the protocol part.
- BINDINGS: replace one remaining HTTP URL with HTTPS.
  Issue: https://github.com/pycurl/pycurl/issues/892
- BINDINGS: fix a broken link.
- BINDINGS: follow a refresh content redirect.
- KNOWN_BUGS: whitespace.

Closes #19911

docs/BINDINGS.md

@@ -49,7 +49,7 @@ Clojure: [clj-curl](https://github.com/lsevero/clj-curl) by Lucas Severo
 
 [Fortran](https://github.com/interkosmos/fortran-curl) Written by Philipp Engel
 
-[Gambas](https://gambas.sourceforge.net/)
+[Gambas](https://gambaswiki.org/website/en/main.html)
 
 [glib/GTK+](https://web.archive.org/web/20100526203452/atterer.net/glibcurl) Written by Richard Atterer
 
@@ -102,7 +102,7 @@ Bailiff and Bálint Szilakszi,
 
 [PureBasic](https://web.archive.org/web/20250325015028/www.purebasic.com/documentation/http/index.html) uses libcurl in its "native" HTTP subsystem
 
-[Python](http://pycurl.io/) PycURL by Kjetil Jacobsen
+[Python](https://github.com/pycurl/pycurl) PycURL by Kjetil Jacobsen
 
 [Python](https://pypi.org/project/pymcurl/) mcurl by Ganesh Viswanathan
 
@@ -112,7 +112,7 @@ Bailiff and Bálint Szilakszi,
 
 [Rexx](https://rexxcurl.sourceforge.net/) Written Mark Hessling
 
-[Ring](https://ring-lang.sourceforge.io/doc1.3/libcurl.html) RingLibCurl by Mahmoud Fayed
+[Ring](https://ring-lang.github.io/doc1.24/libcurl.html) RingLibCurl by Mahmoud Fayed
 
 RPG, support for ILE/RPG on OS/400 is included in source distribution