gnu: Add ghc-reducers.

* gnu/packages/haskell.scm (ghc-reducers): New variable.

gnu: Add ghc-semigroupoids.

* gnu/packages/haskell.scm (ghc-semigroupoids): New variable.

gnu: Add ghc-profunctors.

* gnu/packages/haskell.scm (ghc-profunctors): New variable.

gnu: Add ghc-extra.

* gnu/packages/haskell.scm (ghc-extra): New variable.

gnu: Add ghc-polyparse.

* gnu/packages/haskell.scm (ghc-polyparse): New variable.

gnu: Add HScolour.

* gnu/packages/haskell.scm (hscolour): New variable.

gnu: Add ghc-comonad.

* gnu/packages/haskell.scm (ghc-comonad): New variable.

gnu: Add ghc-distributive.

* gnu/packages/haskell.scm (ghc-distributive): New variable.

gnu: Add ghc-cereal.

* gnu/packages/haskell.scm (ghc-cereal): New variable.

gnu: Add ghc-zip-archive.

* gnu/packages/haskell.scm (ghc-zip-archive): New variable.

gnu: Add ghc-css-text.

* gnu/packages/haskell.scm (ghc-css-text): New variable.

gnu: Add ghc-aeson.

* gnu/packages/haskell.scm (ghc-aeson): New variable.

gnu: Add ghc-attoparsec.

* gnu/packages/haskell.scm (ghc-attoparsec): New variable.

gnu: Add ghc-scientific.

* gnu/packages/haskell.scm (ghc-scientific): New variable.

gnu: Add ghc-tasty-ant-xml.

* gnu/packages/haskell.scm (ghc-tasty-ant-xml): New variable.

gnu: Add ghc-tasty-smallcheck.

* gnu/packages/haskell.scm (ghc-tasty-smallcheck): New variable.

gnu: Add ghc-smallcheck.

* gnu/packages/haskell.scm (ghc-smallcheck): New variable.

gnu: Add ghc-tasty-golden.

* gnu/packages/haskell.scm (ghc-tasty-golden): New variable.

gnu: Add ghc-temporary-rc.

* gnu/packages/haskell.scm (ghc-temporary-rc): New variable.

gnu: Add ghc-clock.

Add ghc-clock, which depends indirectly on ghc-clock-bootstrap for its
test suite.

* gnu/packages/haskell.scm (ghc-clock): New variable.