haskell-amqp-conduit: broken on GHC 7.8.x because of dependency on mtl 2.2.x

pkgs/development/haskell-modules/configuration-ghc-7.8.x.nix

···
   seqid = super.seqid_0_1_0;
   seqid-streams = super.seqid-streams_0_1_0;
 
-  # https://github.com/ivan-m/monad-levels/issues/1
-  monad-levels = dontDistribute super.monad-levels;
+  # Requires mtl 2.2.x: https://github.com/tatac1/amqp-conduit/issues/1
+  amqp-conduit = markBroken super.amqp-conduit;
 
 }