Merge pull request #4589 from bosu/k2pdfopt

New package: k2pdfopt - mobile PDF/DJVU optimizer
hoogle: make sure the package follows the haskell-packages.nix conventions
idris: re-generate expression with cabal2nix
hoogle-4.2.34: re-generate expression with cabal2nix
haskell-pandoc-citeproc: remove duplicate 'default.nix' file

We already have version 0.6 in 0.6.nix.
haskell-pandoc-citeproc: re-generate expression(s) with cabal2nix
remove unused parameter from nixos module that is causing trouble with nixops 1.2
haskell-Decimal: add version 0.4.2
Upgrade: Enlightenment E19: 0.19.0 -> 0.19.1
Introduced haskellPackages.extra
Merge pull request #4592 from aycanirican/haskellPackages.extra

Introduced haskellPackages.extra
systemd: include name of the unit when generating nix store path
haskell-hspec-meta: update to version 1.12.0
haskell-hspec: update to version 1.12.0
haskell-hspec2: update to version 0.5.0
haskell-monadloc-pp: update to version 0.3.1
haskell-pango: update to version 0.13.0.3
haskell-rest-gen: update to version 0.16.0.3
haskell-rethinkdb: update to version 1.15.1.0
haskell-sdl2: update to version 1.1.3