Support new license types introduced in Cabal 1.22.x.
Support new license types introduced in Cabal 1.22.x.

Fixes https://github.com/NixOS/cabal2nix/issues/161.

bennofs/cabal2nix,Fuuzetsu/cabal2nix,gridaphobe/cabal2nix,psibi/cabal2nix,dmalikov/cabal2nix,jb55/cabal2nix,spencerjanssen/cabal2nix