[Debian GNUstep maintainers] Moving away from Alioth

[Yavor Doganov]

We should seriously consider migrating everything as Alioth is being
deprecated.  IIRC, the mailing list will stop working in February and
the host will be shut down completely in May.

See https://wiki.debian.org/Salsa/Doc and the recent annoucements at
d-d-a, many packages are moving.

I'm mostly worried about the mailing list as it appears in the
Maintainer: field.  We don't use Alioth's tracker, AFAICT, and we
don't have any web pages.  So what has to be moved is the Git
repositories and the mailing list.  Are there any cron jobs that are
being run for us at Alioth?  I don't have any.  We've never set up
any custom hooks so we should be fine.