Remove code specific to building with GHC 7.4

Cabal/Distribution/Compat/Binary.hs

@@ -17,10 +17,6 @@ module Distribution.Compat.Binary
 #endif
        ) where
 
-#if __GLASGOW_HASKELL__ < 706
-import Prelude hiding (catch)
-#endif
-
 import Control.Exception (catch, evaluate)
 #if __GLASGOW_HASKELL__ >= 711
 import Control.Exception (pattern ErrorCall)

Cabal/Distribution/Compat/Environment.hs

@@ -51,13 +51,6 @@ getEnvironment = fmap upcaseVars System.getEnvironment
 getEnvironment = System.getEnvironment
 #endif
 
-#if __GLASGOW_HASKELL__ < 706
--- | @lookupEnv var@ returns the value of the environment variable @var@, or
--- @Nothing@ if there is no such value.
-lookupEnv :: String -> IO (Maybe String)
-lookupEnv name = (Just `fmap` System.getEnv name) `catchIO` const (return Nothing)
-#endif /* __GLASGOW_HASKELL__ < 706 */
-
 -- | @setEnv name value@ sets the specified environment variable to @value@.
 --
 -- Throws `Control.Exception.IOException` if either @name@ or @value@ is the