Update nix requirement from 0.16 to 0.19

[dependabot-preview]

Updates the requirements on nix to permit the latest version.

Changelog

Sourced from nix's changelog.

[0.19.0] - 6 October 2020

Added

• Added Netlink protocol families to the SockProtocol enum (#1289)
• Added clock_gettime, clock_settime, clock_getres, clock_getcpuclockid functions and ClockId struct. (#1281)
• Added wrapper functions for PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP. (#1300)
• Add support for Vsock on Android rather than just Linux. (#1301)
• Added TCP_KEEPCNT and TCP_KEEPINTVL TCP keepalive options. (#1283)

Changed

• Expose SeekData and SeekHole on all Linux targets (#1284)
• Changed unistd::{execv,execve,execvp,execvpe,fexecve,execveat} to take both &[&CStr] and &[CString] as its list argument(s). (#1278)
• Made unistd::fork an unsafe funtion, bringing it in line with libstd's decision. (#1293)

Fixed

Removed

[0.18.0] - 26 July 2020

Added

• Added fchown(2) wrapper. (#1257)
• Added support on linux systems for MAP_HUGE_SIZE family of flags. (#1211)
• Added support for F_OFD_* fcntl commands on Linux and Android. (#1195)
• Added env::clearenv(): calls libc::clearenv on platforms where it's available, and clears the environment of all variables via std::env::vars and std::env::remove_var on others. (#1185)
• FsType inner value made public. (#1187)
• Added unistd::setfsuid and unistd::setfsgid to set the user or group identity for filesystem checks per-thread. (#1163)
• Derived Ord, PartialOrd for unistd::Pid (#1189)
• Added select::FdSet::fds method to iterate over file descriptors in a set. (#1207)
• Added support for UDP generic segmentation offload (GSO) and generic receive offload (GRO) (#1209)
• Added support for sendmmsg and recvmmsg calls (#1208)
• Added support for SCM_CREDS messages (UnixCredentials) on FreeBSD/DragonFly (#1216)
• Added BindToDevice socket option (sockopt) on Linux

Commits

• 074b5ae Merge #1307
• 89b029b Merge #1283
• fde7181 Add support for TCP_KEEPCNT and TCP_KEEPINTVL TCP keepalive options.
• 566e2d7 Merge #1303
• b67883b Release v0.19.0.
• 59e33bc Merge #1301
• c573956 Support vsock on Android as well as Linux.
• 462e4bf Renable the ScmTimestamp test on FreeBSD i386
• 7e46b95 Merge #1296
• 7ed2820 Merge #1300
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

[dependabot-preview]

Superseded by #85.