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

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

These checks were done:

- built on NixOS
- /nix/store/c48vhaf6wqmra1g6sv4hv3i6vqlw7ll1-wireguard-tools-0.0.20180519/bin/wg passed the binary check.
- /nix/store/c48vhaf6wqmra1g6sv4hv3i6vqlw7ll1-wireguard-tools-0.0.20180519/bin/wg-quick passed the binary check.
- 2 of 2 passed binary check by having a zero exit code.
- 0 of 2 passed binary check by having the new version present in output.
- found 0.0.20180519 with grep in /nix/store/c48vhaf6wqmra1g6sv4hv3i6vqlw7ll1-wireguard-tools-0.0.20180519
- directory tree listing: https://gist.github.com/64bccf9c57ca84c49486890ccbf17239
- du listing: https://gist.github.com/f28d6cfd8bcbf6ab1a6c39ad40ce1606

wireguard: 0.0.20180514 -> 0.0.20180519