Merge branch 'master' into staging

* master: (71 commits)
  xen: enable parallel building
  spice: 0.13.3 -> 0.14.0
  powerline-rs: 0.1.7 -> 0.1.8 (#41736)
  xidlehook: 0.4.6 -> 0.4.8 (#41094)
  serf: update scons patch, enable kerberos on darwin
  firefox-bin: Add ffmpeg to lib path
  firefox-beta-bin: 61.0b10 -> 61.0b12
  firefox-devedition-bin: 61.0b10 -> 61.0b12
  wireguard-go: assign yegortimoshenko as maintainer
  wireguard-go: 0.0.20180519 -> 0.0.20180531
  zfs: Fix "zfs-sync" for modern systemd
  nixos/memcached: added simple set/get test
  jenkins: 2.89.4 -> 2.107.3 (#41618)
  focuswriter: 1.6.12 -> 1.6.13 (#41567)
  ne: 3.0.1 -> 3.1.1 (#41536)
  libpqxx: 6.2.3 -> 6.2.4 (#41547)
  mate.mate-applets: 1.20.1 -> 1.20.2 (#41546)
  mate.mate-themes: 3.22.16 -> 3.22.17 (#41541)
  nixos/munge: run munge as user munge instead of root. (#41509)
  pstoedit: 3.71 -> 3.73 (#41528)
  ...