Merge branch 'master' into staging

* master: (28 commits)
  go_1_9: skip flaky TestWaitGroupMisuse2
  erlangR18: fix patch hashes with fetchpatch
  xml2: replace dead links
  nixos/pam: fix docs about path to u2f_keys file
  cinelerra: add a note about parallel building
  msmtp: install docs and examples (#31769)
  kernel: Fix out-of-tree modules on aarch64
  nixos/tests/acme: update terms of service to fix test
  gixy: init at 0.1.8
  pythonPackages.ConfigArgParse: 0.9.3 -> 0.12.0, refactor, move to python-modules
  mono: init at 4.8
  wal-g: fix license so not to break evaluation
  wal-g: init at 0.1.2
  maintainers: add backuitist
  nixos/prometheus: Correct documentation for external_labels
  spidermonkey: replace broken links
  vagrant: removed custom rake gem
  vagrant: 2.0.0 -> 2.0.1
  nixos/prometheus: add external_labels option
  nixos/prometheus: add scrape_configs.honor_labels
  ...