tests.haskell*: move into tests.haskell set

This will make it easier to add all haskell related tests to the haskell
hydra jobset without updating a list of tests in two places.

pkgs/test/haskell/documentationTarball/default.nix

@@ -0,0 +1,17 @@
+{ pkgs, haskellPackages }:
+
+let
+  drv = haskellPackages.vector;
+  docs = pkgs.haskell.lib.documentationTarball drv;
+
+in pkgs.runCommand "test haskell.lib.documentationTarball" { } ''
+  tar xvzf "${docs}/${drv.name}-docs.tar.gz"
+
+  # Check for Haddock html
+  find "${drv.name}-docs" | grep -q "Data-Vector.html"
+
+  # Check for source html
+  find "${drv.name}-docs" | grep -q  "src/Data.Vector.html"
+
+  touch "$out"
+''