Nixpkgs: Torch is busted

[Fresheyeball]

https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/science/machine-learning/torch/default.nix

This shit is broke. We should mark it broke, or fix it.

[coreyoconnor]

to be pedantic: Dependencies in the torch distribution are already marked as broken. One cannot currently build a top level torch derivation as it's deps are marked broken.

Does this constitute being marked broken already? Not sure.

Does being marked broken for such a long time mean we should remove it? I think so.

[teto]

I mentioned this issue last week in
https://github.com/NixOS/nixpkgs/issues/56398#issuecomment-542085717. It could
be reimplemented by using the new architecture.

[bhipple]

Not only is it broken, it's completely unmaintained and dead upstream:

https://github.com/torch/torch7#development-status

As of 2019, the Torch-7 community is close to non-existent.

It appears that the useful bits have been ported over to pytorch, and the rest left to rot. Let's remove the remains.