Drop redundant `-fno-warn-deprecations`

Doesn't seem to have any effect with GHC HEAD.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Add explicit `{-# LANGUAGE CPP #-}` pragmas

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
`M-x untabify` & `M-x delete-trailing-whitespace`

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Modernize and refactor `haskell98.cabal`

 - Update to `cabal-version>=0.10`
 - add missing `Setup.hs`
 - add `Prelude` category
 - update version constraints
 - update bug-reports URL
 - add `repository this`

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>