Suppress some warnings

Distribution/Simple/Install.hs

 {-# OPTIONS -cpp #-}
+{-# OPTIONS_GHC -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
+-- for details
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Distribution.Simple.Install