custom-scripts: also work around issues (see previous commit) in packages for the xfce4 desktop as well as more gnome and mate packages
custom-scripts: only workaround systemd-sysv removal issues on sid, jessie + experimental
instances/piuparts.conf.pejacevic: Results from debsums on wheezy2jessie and wheezy2bpo2jessie are not being ignored anymore as #744398 has been fixed thanks to Axel Beckert.
custom-scripts: fix bashism