sd-bus: check return value of asprintf()

Check for OOM conditions of asprintf() in bus_set_address_user().
man: SyslogIdentifier= has an effect on journal logging too
logind: mount per-user tmpfs with 'smackfsroot=*' for smack enabled systems
bus-policy: move name list iteration to policy users

We need to figure out which of the possible names satisfied the policy,
so we cannot do the iteration in check_policy_item() but have to leave it
to the users.

Test cases amended accordingly.
sd-dhcp6-lease: Name the structure containing IAADDR data

With this change the DHCP6_OPTION_IAADDR_LEN define can be removed in
favor of using sizeof(). Using the name of the struct and sizeof()
makes it clearer how much and what data is being copied from the
DHCPv6 message.
socket-proxyd: Unchecked return value from library

CID 1237543 (#1 of 1): Unchecked return value from library
(CHECKED_RETURN)
bus-proxy: allow getpeersec() to fail

getpeersec() will fail for non-SELinux enabled machines, so don't make that
a hard error.
update TODO
service: enter SERVICE_STOP_SIGTERM state after getting "STOPPING=1"

SERVICE_STOP would mean we're running the ExecStop command. That's not
the case with "STOPPING=1".
Instead we should enter the same state as if we just told the service
to stop, i.e. SERVICE_STOP_SIGTERM.

This fixes a bug where voluntarily exiting services would hang around in
deactivating state until timeout.
man: document the new "rescue" kernel command line option
sd-journal: do not reset sd_j_enumerate_unique position on error

systemctl would call sd_j_enumerate_unique() interleaved with
sd_j_next(). But the latter can remove a file if it detects an
error in it. In those circumstances sd_j_enumerate_unique would
restart with the first file in hashmap. With many corrupted files
sd_j_enumerate_unique might iterate over the list multiple times.

Avoid this by jumping to the next file in unique list if possible,
or setting a flag that tells sd_j_enumerate_unique that it is done
otherwise.
sd-journal: change check to assert

As of 0f99f74a14 'sd-journal: verify that object start with the field
name' this condition should never happen.
sd-journal: fix sd_journal_enumerate_unique skipping values

sd_journal_enumerate_unique will lock its mmap window to prevent it
from being released by calling mmap_cache_get with keep_always=true.
This call may return windows that are wider, but compatible with the
parameters provided to it.

This can result in a mismatch where the window to be released cannot
properly be selected, because we have more than one window matching the
parameters of mmap_cache_release. Therefore, introduce a release_cookie
to be used when releasing the window.

https://bugs.freedesktop.org/show_bug.cgi?id=79380
journalctl: use pager for --list-boots
systemctl: remove casts in formatting
man: clarify what "microsoft" and "oracle" stand for

https://bugzilla.redhat.com/show_bug.cgi?id=1150477
Update TODO
build-sys: use -Wno-typedef-redefinition only for clang

Our checks for -Wno-xxx switches do not work with gcc [1].

[1] https://gcc.gnu.org/wiki/FAQ#wnowarning
build-sys: use -Wno-gnu-variable-sized-type-not-at-end under clang

Otherwise we get useless warnings about journal code.
systemd-hibernate-resume@.service: remove unnecessary ordering

They were left from an early review iteration, when hibernate-resume
functionality was intended to work also outside of initramfs.
Now this is not the case, and these dependencies became redundant
as systemd-fsck-root.service can never be part of initramfs, and
systemd-remount-fs.service makes little sense in it.