Enable all extensions in xmobar by default.
Enable all extensions in xmobar by default.

https://github.com/NixOS/nixpkgs/pull/2728

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