upgrade links to HTTPS

upgrade links to HTTPS

http://infozip.sourceforge.net/ is sadly not having HTTPS access
enabled. Shoutout to somebody with admin access for this project:
It would be nice to enable it and thus allowing secure access to
these pages via https://infozip.sourceforge.io/ . The option has
been there for a while now:
  https://sourceforge.net/blog/introducing-https-for-project-websites/

also:
- follow permanent redirects
- add ending slashes