batctl: 2018.0 -> 2018.1

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/batctl/versions.

These checks were done:

- built on NixOS
- ran ‘/nix/store/8djn6psqrxjc66chnig215c5z8il9zaw-batctl-2018.1/bin/batctl -h’ got 0 exit code
- found 2018.1 with grep in /nix/store/8djn6psqrxjc66chnig215c5z8il9zaw-batctl-2018.1
- directory tree listing: https://gist.github.com/13f600b1fb0404e8b5b78d0e2e32f5c5