Add a version suffix even when there are no local changes

We always add some extra files, at least the Apertis component,
plus copyright scanning results. Since those are intended to end up
in the source package, we should append a version suffix regardless
of any other actual changes we add on top.

Since these changes are an addition of metadata only, co0 seems a
good enough starting version.

Instead of dch, we use a custom changelog modification implementation.
This is because dch insists on launching an interactive editor when
a changelog is finalised.

Apertis: T7556

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>