nspawn: Add try-{host,guest} journal link modes

--link-journal={host,guest} fail if the host does not have persistent
journalling enabled and /var/log/journal/ does not exist. Even worse, as there
is no stdout/err any more, there is no error message to point that out.

Introduce two new modes "try-host" and "try-guest" which don't fail in this
case, and instead just silently skip the guest journal setup.

Change -j to mean "try-guest" instead of "guest", and fix the wrong --help
output for it (it said "host" before).

Change systemd-nspawn@.service.in to use "try-guest" so that this unit works
with both persistent and non-persistent journals on the host without failing.

https://bugs.debian.org/770275
busctl: add options to control message header flags when invoking methods
busctl: add --timeout= option to specify method call timeout
man: add emacs header to get correct indention in nxml-mode for the manpage XML files that use 2ch indenting

In the long run we really should figure out if we want to stick with 8ch
or 2ch indenting, and not continue with half-and-half. For now, just
make emacs aware of the files that use 2ch indenting.
man: don't mix 2ch and 8ch indentation in busctl.xml
selinux-access: fix broken ternary operator

it seems to be a typo introduced by ebcf1f97de4f6b1580ae55eb56b1a3939fe6b602
-                _r = selinux_access_check(_b, _m, _u->source_path ?:_u->fragment_path, (permission), &_error); \
+        ({ Unit *_unit = (unit); selinux_generic_access_check(bus,message, _unit->fragment_path ?: _unit->fragment_path, permission,error); })
missing: add __NR_getrandom for a few more archs

Mips has getrandom() too, but there's just too many variants
for me too care. Either someone who cares does it, or they get
compile-time warnings with old kernel headers.
missing: add IFLA_BRPORT_LEARNING and friends

IFLA_BRPORT_LEARNING was added in v3.10-rc4-583-g9ba18891f7,
and IFLA_BRPORT_UNICAST_FLOOD in v3.10-rc4-584-g867a59436f.
Do not check for existence of remote binaries

systemd-run would fail when run with -M or -H and an absolute path,
if this path did not exists locally. Allow it to continue, since we
don't have a nice way of checking if the binary exists remotely.

The case where -M or -H is used and a local path is unchanged, and we
still iterate over $PATH to find the binary. We need to convert to an
absolute path, and we don't have a nice mechanism to check remotely,
so we assume that the binary will be located in the same place locally
and remotely.

http://lists.freedesktop.org/archives/systemd-devel/2014-November/025418.html
man/logind.conf.xml: make consistent with default logind.conf

https://bugs.freedesktop.org/show_bug.cgi?id=86263
nspawn: ignore EEXIST when mounting tmpfs

commit 79d80fc1466512d0ca211f4bfcd9de5f2f816a5a introduced a regression that
prevents mounting a tmpfs if the mount point already exits in the container's
root file system. This commit fixes the problem by ignoring EEXIST.
systemctl: show BindsTo/BoundBy in list-dependencies

Suggested-by: Peter Mattern <matternp@arcor.de>

http://lists.freedesktop.org/archives/systemd-devel/2014-November/025437.html