nspawn: add --register=yes|no switch to optionally disable registration of the container with machined
util: drop parse_user_at_host() since its unused now
util: modernize readlink_malloc() a bit
machined: optionally, allow registration of pre-existing units (scopes
or services) as machine with machined
efi: fix Undefined reference efi_loader_get_boot_usec when EFI support is disabled
logind: use session_get_state() to get sessions state of the user

In function user_get_state() remove the session_is_active() check, just
count on the session_get_state() function to get the correct session
state.

session_is_active() may return true before starting the session scope
and user service, this means it will return true even before the creation
of the session fifo_fd which will produce incorrect states.

So be consistent and just use session_get_state().
update TODO
machined: fix enumeration of existing machines on restart
units: make use of nspawn's --keep-unit switch in systemd-nspawn@.service
journald: log provenience of signals
logind: always kill session when termination is requested

KillUserProcesses=yes/no should be ignored when termination is
explicitly requested.
logind: ignore PropertiesChanged signals for jobs

Otherwise we get a (harmless) message like:
systemd-logind[30845]: Failed to process message [type=signal sender=:1.36 path=/org/freedesktop/systemd1/job/4674 interface=org.freedesktop.DBus.Properties member=PropertiesChanged signature=sa{sv}as]: Invalid argument
machinectl: add new "machinectl reboot" call
test: fix "make check"

Let's remove the tests for cg_path_get_machine_name(), since they no
longer operate solely on the cgroup path, but actually look up data in
/run. Since we have a test for cg_pid_get_machine_name() this shouldn't
be too much of a loss.
nspawn: newer kernels (>= 3.14) allow resetting the audit loginuid, make use of this
pager: support SYSTEMD_LESS environment variable

This allows customization of the arguments used by less. The main
motivation is that some folks might not like having --no-init on every
invocation of less.
man: use xinclude to de-deduplicate common text

I only tested with python-lxml. I'm not sure if xml.etree should be
deprecated.
build-sys: add less-variables.xml to EXTRA_DIST
build-sys: make lxml required when generating indices

Since the manpage indices generated without lxml would be missing some
parts, it doesn't make sense to keep lxml optional anymore.
update TODO (add section for things to fix before 209)