Libwebsockets: add and use 4.2.0 as default

[Mindavi]

Motivation for this change

Add a libwebsockets version 4.2.0 and make it default. I think it's most logical to track the latest version, and I got everything to build.

Depends on #123135 for a successful ttyd build.

Please also look at the commit messages, I'm not sure if they're fully conforming the standards.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
  • ardour: already broken on hydra
  • ttyd: bumping version makes it compile (ttyd: 1.6.1 -> 1.6.3 #123135)
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[r-rmcgibbo]

Result of nixpkgs-review pr 123137 at 7d0eb78 run on aarch64-linux 1

1 package failed to build:

• ttyd

3 packages skipped due to time constraints:

• ardour
• collectd
• collectd-data

8 packages built successfully:

• domoticz
• driftnet
• libwebsockets (libwebsockets_4_2)
• libwebsockets_3_1
• libwebsockets_3_2
• libwebsockets_4_0
• libwebsockets_4_1
• mosquitto

Note that build failures may predate this PR, and could be nondeterministic or hardware dependent.
Please exercise your independent judgement. Does something look off? Please file an issue or reach out on IRC.

---

Result of nixpkgs-review pr 123137 at 0891da9 run on x86_64-linux 1

2 packages marked as broken and skipped:

• libwebsockets_4_0
• libwebsockets_4_1

2 packages failed to build:

• ardour
• ttyd

8 packages built successfully:

• collectd
• collectd-data
• domoticz
• driftnet
• libwebsockets (libwebsockets_4_2)
• libwebsockets_3_1
• libwebsockets_3_2
• mosquitto

Note that build failures may predate this PR, and could be nondeterministic or hardware dependent.
Please exercise your independent judgement. Does something look off? Please file an issue or reach out on IRC.

[fabaff]

Mosquitto seems the only one that requires the 3.x serie but that's something for another PR.

[Mindavi]

I was already wondering if I should keep around all those old versions. Thanks for pushing me over the edge to do so :). Mosquitto compiles fine with libwebsockets 4.2, so we can bump that one / move to the default version and then remove all the 3.x series, I think. Will prepare a PR for that.

[Mindavi]

@fabaff got some time to look at this? Should be good to go.