gpt-auto-generator: rename root device node symlink to /dev/gpt-auto-root

Before it was placed in /dev/disk/by-id, which makes it a bit too much
API. However, it's mostly an implementation detail for now, hence move
it out of the stable block device dir.
core: support globbing matches in DeviceAllow= when checking for device groups
nspawn: allow using kdbus from nspawn containers
nspawn: fix argv[0] for getent
logind: Do not fail display count if a device has no parent

udev_device_get_parent() may return NULL when the device doesn't have a
parent, as is the case with (for example) /sys/devices/virtual/drm/ttm.

Also, log an actual error message instead of "-12 displays connected".
hostnamed: minor improvements in context_write_data_other()

Prepare context_write_data_other() and rename it to
context_write_data_machine_info()
hostnamed: expose OperatingSystemPrettyName and OperatingSystemCPEName on the bus
hostnamectl: read OS pretty_name and cpe_name from remote
build-sys: sign releases
fstab-generator: when running in a container, ignore fstab entries referring to device nodes

Since these device nodes will never appear in the container anyway
there's no point in waiting for them.

This makes it easier to boot images generated with general purpose
installers like Anaconda which unconditionally populate /etc/fstab to
boot in containers.
update TODO
bus: replace sd_bus_label_{escape,unescape}() by new sd_bus_path_{encode,decode}()

The new calls work similarly, but enforce a that a common, fixed bus
path prefix is used.

This follows discussions with Simon McVittie on IRC that it should be a
good idea to make sure that people don't use the escaping applied here
too wildly as anything other than the last label of a bus path.
update TODO
NEWS: prepare for release 211
man: improve nspawn's --user= documentation
build-sys: prepare release 211
NEWS: update
build-sys: when I upload the tarball, don't run the whole distcheck thing again

I run this anyway, and given how slow it is now due to -flto, let's make
my workflow a bit faster...
NEWS: fix typo

sittings -> settings
build-sys: we still want to rebuild the tarball though on upload