debian: Remove packaging from upstream repository.

Debian packaging for GnuPG is handled in debian git repositories, and
doesn't belong here in the upstream repository. The packaging was
significantly out of date anyway.

If you're looking for debian packaging for the 1.4 branch of GnuPG,
please use the following git remote:

https://anonscm.debian.org/git/pkg-gnupg/gnupg1.git

• Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>