debian/changelog: Sync with Debian

Sync with Debian, and start preparing for 3.5.0~rc1-1 upload to
unstable.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
debian: Add syslog-ng-core lintian overrides

Lintian has a bug (#727683) that triggers an error by mistake, lets
ignore that.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
debian: Ship a few more directories in syslog-ng-core

Ship /etc/syslog-ng/conf.d/ and /var/lib/syslog-ng/ in the
syslog-ng-core package. We already had this before, but lost the patch
somewhere.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
debian: Change maintainer to the alioth list

Maintainer changed to syslog-ng-maintainers@lists.alioth.debian.org,
added GCS, Sasa and myself to Uploaders.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>
debian: Use deb-systemd-invoke in prerm, if available

Use deb-systemd-invoke in prerm to stop syslog.socket, as that respects
policy.d, while systemctl does not.

Signed-off-by: Gergely Nagy <algernon@balabit.hu>