###### Motivation for this change
Update to latest upstream version
###### Things done
* [ ] Tested using sandboxing ([nix.useSandbox](http://nixos.org/nixos/manual/options.html#opt-nix.useSandbox) on NixOS, or option `sandbox` in [`nix.conf`](http://nixos.org/nix/manual/#sec-conf-file) on non-NixOS linux)
* Built on platform(s)
* [x] NixOS
* [ ] macOS
* [ ] other Linux distributions
* [ ] Tested via one or more NixOS test(s) if existing and applicable for the change (look inside [nixos/tests](https://github.com/NixOS/nixpkgs/blob/master/nixos/tests))
* [ ] Tested compilation of all pkgs that depend on this change using `nix-shell -p nix-review --run "nix-review wip"`
* [x] 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
* [x] Fits [CONTRIBUTING.md](https://github.com/NixOS/nixpkgs/blob/master/.github/CONTRIBUTING.md).
###### Notify maintainers
cc @worldofpeace @tfc @jtraue
I am not sure if we still need the old packages, nothing explicitly
depends on polyml56 or polyml57 according to a grep, not sure if
external packages might (hol and isabelle depend on polyml, the latest
version).
New libffi doesn't have FFI_SYSV for x86/64 unix, this pulls in the
commit for the upstream version which fixes it, and ports that patch to
the 5.7 version. The 5.6 version is unchanged.
For ZHF: #80379
Also updates the matchable egg (used by egg2nix) from 1.0 -> 1.1 and
removes trailing slashes from the path prefix variables passed to
wrapProgram (they're unnecessary and only result in doubled-up slashes
in the values).
I din't try to pinpoint the exact commit, but we started getting:
> The extension smart is not supported for docbook
Reading pandoc docs, I can't see what use to us "smart" could be
when writing the in-between docbook (to be converted to html).
https://pandoc.org/MANUAL.html#extension-smart
