NUT v2.8.0 (un-signed)

This is a re-post of the release artifacts to keep download URLs based on original vX.Y.Z git tag pattern, as used by distro recipes, intact. Such URLs got broken after addressing issue #1410, as reported later in issue #1971.

For release details, please see https://github.com/networkupstools/nut/releases/tag/v2.8.0-signed