byacc: 20180525 -> 20180609

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

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

These checks were done:

- built on NixOS
- /nix/store/rngxfbcnpk0n5v16msm7dhg609xfg5jp-byacc-20180609/bin/yacc passed the binary check.
- 1 of 1 passed binary check by having a zero exit code.
- 0 of 1 passed binary check by having the new version present in output.
- found 20180609 with grep in /nix/store/rngxfbcnpk0n5v16msm7dhg609xfg5jp-byacc-20180609
- directory tree listing: https://gist.github.com/a6550f00724283aca52496de32c95794
- du listing: https://gist.github.com/85e15144de69a0381160d89701d1b858