Merge branch 'master' into staging

* master: (153 commits)
  coqPackages.contribs.aac-tactics: enable for Coq 8.7 and 8.8 (#41351)
  haskell.packages.ghcjs.terminfo: Bump version (#41337)
  nixos/mpd: allow services.mpd.dbFile to be null
  prometheus-snmp-exporter: 0.9.0 -> 0.11.0 (#41363)
  tdesktopPackages.preview: 1.2.24 -> 1.3.0
  signal-desktop: Refactor the package description
  rrootage: init at 0.23a
  bulletml: init at 0.0.6
  signal-desktop: Fix a possible crash when saving an attachment
  linux_rpi: More downstream device tree name fixups
  nixos/sd-image-raspberrypi: Support Raspberry Pi Zero
  U-Boot: Add ubootRaspberryPiZero variant
  U-Boot: 2018.03 -> 2018.05
  linux_rpi: 1.20171029 -> 1.20180417
  raspberrypifw: 1.20180328 -> 1.20180417
  scite: 3.7.5 -> 4.0.5 (#41345)
  neo4j: 3.3.4 -> 3.4.0 (#41338)
  bat: 0.3.0 -> 0.4.1 (#41348)
  perlPackages.Git: init at 0.42
  nodePackages_8_x.pnpm: wrap nodejs.passthru.python
  ...