apmplanner2: fix build against qt 5.12

[peterhoeg]

Motivation for this change

Couple of things:

1. Apply a patch to make it compile with Qt 5.12
2. stdenv.mkDerivation -> mkDerivation
3. name -> pname, version

I don't actually use this application - it was part of a cleanup for a new KDE version that touched Qt which prompted this PR.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• 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 nix-review --run "nix-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.

Notify maintainers

cc @wucke13

[mmahut]

@GrahamcOfBorg build apmplanner2

[wucke13]

Seems to work fine, thanks for the contribution!