altcoins.bitcoin: 0.16.0 -> 0.16.1

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

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

These checks were done:

- built on NixOS
- /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/bitcoind passed the binary check.
- /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/bitcoin-cli passed the binary check.
- /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/bitcoin-tx passed the binary check.
- /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/test_bitcoin passed the binary check.
- /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/bench_bitcoin passed the binary check.
- Warning: no invocation of /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/bitcoin-qt had a zero exit code or showed the expected version
- Warning: no invocation of /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1/bin/test_bitcoin-qt had a zero exit code or showed the expected version
- 5 of 7 passed binary check by having a zero exit code.
- 0 of 7 passed binary check by having the new version present in output.
- found 0.16.1 with grep in /nix/store/5fjv944ikyak1s83624ay8i9h4gbs2c0-bitcoin-0.16.1
- directory tree listing: https://gist.github.com/a5e5d745910497ae913d4577342deba5
- du listing: https://gist.github.com/5f62bec50f6ab977a25c8ee0f118cb10