Bug#1079495: mate-screensaver: please don't depend on dbus-x11

[Simon McVittie <smcv@debian.org>]

Package: mate-screensaver
Severity: normal
User: dbus@packages.debian.org
Usertags: dbus-launch

mate-screensaver has a dependency on the dbus-x11 package, but doesn't seem
to use dbus-launch directly.

The dbus-x11 package is unnecessary on typical Debian desktop systems
which have systemd and dbus-user-session installed, and it has some
backwards-compatibility side-effects which are not ideal, so I'm trying to
reduce direct dependencies on it.

If mate-screensaver needs a D-Bus session bus (quite likely), the usual
dependency is:

    default-dbus-session-bus | dbus-session-bus

which in practice can be satisfied by either dbus-user-session or dbus-x11.

Thanks,
    smcv