Merge branch 'master' into staging

Resolved the following conflicts (by carefully applying patches from the both
branches since the fork point):

   pkgs/development/libraries/epoxy/default.nix
   pkgs/development/libraries/gtk+/3.x.nix
   pkgs/development/python-modules/asgiref/default.nix
   pkgs/development/python-modules/daphne/default.nix
   pkgs/os-specific/linux/systemd/default.nix