debian/gbp.conf: some instructions for git-dch
README.source: let's use xz while creating the orig.tar.xz
Imported Upstream version 31.1.1
Merge tag 'upstream/31.1.1'

Upstream version 31.1.1

# gpg: Unterschrift vom Fr 12 Sep 2014 21:33:22 CEST mittels RSA-Schlüssel ID 251D1DB0
# gpg: Korrekte Unterschrift von "Carsten Schoenert <c.schoenert@t-online.de>"