systemd: merge branch systemd into master

Update systemd code from upstream. In the meantime, two
patches that we applied early in NetworkManager core were
applied in upstream systemd too. So, resync.

diff --cc src/systemd/src/basic/log.h
Simple merge

diff --cc src/systemd/src/basic/macro.h
Simple merge

diff --cc src/systemd/src/basic/util.h
Simple merge

diff --cc src/systemd/src/libsystemd-network/lldp-neighbor.c
Simple merge