Imported Upstream version 2.5
Merge tag 'upstream/2.5'

Upstream version 2.5
Upstream license was changed to AGPL-3.0
Make .links file match actual binary package name
Update manpage soft links target

The main manpage is installed as thc-ipv6.8 to match binary package
name. Update link files to target the new name.
Keep links to manpage sorted
Add manpage links for new tools
Override lintian warning manpage-has-bad-whatis-entry
Patches refreshed
Update changelog