rev.84

1. Fixes for PHP 8.1
2. Fixes for some security issues (potential and not so)
3. fluxbb/fluxbb#225 and fluxbb/fluxbb#236
4. Remove discontinued AOL IM, Yahoo Messenger and MSN in profiles
5. New Private Messaging System v1.9.2
6. Media.js v2.6.0
7. Change pagination of topic pages on the forum page
8. Other changes and fixes (read commits 1.5.11.83...1.5.11.84).