bison3: mark low-prio until the check phase is fixed
lightdm updates (merge #574)

Also fixes the situation where some session stuff is written to nix store.
haskell-git-annex: update to version 4.20130802
haskell-MissingH: update to version 1.2.0.1
haskell-numeric-prelude: update to version 0.4.0.3
haskell-shakespeare: update to version 1.0.5.1
haskell-stylish-haskell: update to version 0.5.7.0
haskell-vault: update to version 0.3.0.0