Motivation for this change

Following #78265 I thought I would try and tackle all the dead links listed in Repology, by both updating the ones that were moved and listing explicitly projects that are nowhere to be found. This is still WIP as there are 279 remaining pkgs for me to go through.

List of really dead projects with unfindable homepages and/or source directories (so far):

cernlib (http://cernlib.web.cern.ch)
libesmtp (http://www.stafford.uklinux.net/libesmtp/)
x86info (http://codemonkey.org.uk/projects/x86info/)
zdelta (http://cis.poly.edu/zdelta)

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.