Update vcsh to 2.x

[alerque]

This is rather a shot in the dark. I'm the one that did the work upstream overhauling the build system between 1.x and 2.x so I know what happened there, but I don't know if this packaging is anything like correct.

The major change is that we switched from a home-grown makefile to a regular autotools build with a configure that checks for dependencies and system paths, and a make install that puts it all in standardized locations. All standard things like --prefix when configuring and DESTDIR when installing should would as expected now.

Additionally there are bash and zsh completions that should get installed, but I don't know if this build recipe will handle that or not.

@ttuegel I'm available for questions, and by all means if this doesn't get close feel free to nuke this and handle it however is proper.

Motivation for this change

Upstream release:

https://github.com/RichiH/vcsh/releases/tag/v2.0.1

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"
• 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.

[bobby285271]

I am very sorry I didn't notice the sile update, that should be put in a separate commit, so exactly two commits:

• vcsh: 1.20170915 → 2.0.1
• sile: 0.10.14 → 0.10.15

Otherwise the vcsh package builds and runs, LGTM.

[alerque]

Wow what the heck! That should not have gotten in this squash, I was working on that in another branch. I must have gotten sapped by a Neovim buffer still being open and a :W instead of :w.

[alerque]

That sile update isn't even current! It was from months ago and is already in master. Another update is in progress in #136453, I've removed that from the commit.