nspawn: make host0's MAC address persistent

We still need to make sure that no two MAC addresses are the same, so we use
a logic similar to what is used in udev to generate MAC addresses, and base
it on a hash of the host's machine ID and thecontainer's name.
bus: fix memory leak when kdbus is not enabled
sd-bus: don't look for a 64bit value when we only have 32bit value on reply cookie hash table access

This broke hashtable lookups for the message cookies on s390x, which is
a 64bit BE machine where accessing 32bit values as 64bit and vice versa
will explode.

Also, while we are at it, be a bit more careful when dealing with the
64bit cookies we expose and the 32bit serial numbers dbus uses in its
payload.

Problem identified by Fridrich Strba.
timedated: add SNTP client/query hookup (unused for now)
logind: automatically remove SysV + POSIX IPC objects when the users owning them fully log out
update TODO
nspawn: allow -EEXIST on mkdir_safe /home/${uid}

With systemd 211 nspawn attempts to create the home directory for the
given uid. However, if the home directory already exists then it will
fail. Don't error out on -EEXIST.
nspawn: remove unused variable
networkd: lease - store (up to) one dhcp lease file per interface

This removes an accidentally left-over test fragment.
networkd: fix creation of runtime dirs at startup

This allows us to drop the repeated attempted creations of the runtime dirs during runtime.
networkd: allow more than one static DNS server
machine-id: add --root option to operate on an alternate fs tree

This makes it possible to initialize the /etc/machine-id file on an
arbitrary filesystem hierarchy.  This helps systems that wish to run
this at image creation time in a subdirectory, or from initramfs before
pivot-root is called.

[tomegun: converted to using _cleanup_free_ macros]
man: network - clarify which options may be specified more than once.
machine-id-setup: use path_kill_slashes and modernizations
Do not return -1 (EINVAL) on allocation error
shared: add root argument to search_and_fopen

This adds the same root argument to search_and_fopen that
conf_files_list already has. Tools that use those two functions as a
pair can now be easily modified to load configuration files from an
alternate root filesystem tree.
tmpfiles: add --root option to operate on an alternate fs tree

This makes it possible to initialize or cleanup an arbitrary filesystem
hierarchy in the same way that it would be during system boot.
gpt: introduce root partition type GUIDs for ARM 32bit + ARM 64bit
networkd: fix typo

It's HAVE_SPLIT_USR not HAVE_SPLIT_USER