kbuild, deb-pkg: bump standards version

Latest Debian policy is 3.8.1.
Even if we are not yet compliant to it strive for the latest.

Signed-off-by: maximilian attems <max@stro.at>
Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>