haskell-ghc-mod-5.0.1: use wrapProgram

Use wrapProgram from makeWrapper to wrap ghc-mod and ghc-modi like
haddock. The wrapper code is clearer and hopefully more maintainable. As
a side-effect, the bug where emacs would hang while loading ghc-modi is
fixed.
yesod-auth-hashdb haskell package added
Some additional android runtimes.
Re-generate Haskell packages with cabal2nix.
haddock-2.14.3: enable test suite

https://github.com/NixOS/cabal2nix/pull/86
radvd: Upsate 1.8.1 -> 2.5
nixos/radvd: Convert to a systemd unit

Additionally, remove the automatic initialization of the ipv6 forwarding
sysctl as this should be handled by the end user. This really should not
be an issue as most people running radvd are likely forwarding ipv6
packets.