Fix conditional pragma to work with 6.12

Foreign/Marshal/Alloc.hs

-{-# LANGUAGE CPP #-}
 #if __GLASGOW_HASKELL__ >= 701
 {-# LANGUAGE Safe #-}
 #endif

Foreign/Marshal/Array.hs

-{-# LANGUAGE CPP #-}
 #if __GLASGOW_HASKELL__ >= 701
 {-# LANGUAGE Safe #-}
 #endif

Foreign/Marshal/Utils.hs

-{-# LANGUAGE CPP #-}
 #if __GLASGOW_HASKELL__ >= 701
 {-# LANGUAGE Safe #-}
 #endif

Prelude.hs

+{-# LANGUAGE NoImplicitPrelude, BangPatterns #-}
 #if __GLASGOW_HASKELL__ >= 701
 {-# LANGUAGE Trustworthy #-}
 #endif
 
-{-# LANGUAGE NoImplicitPrelude, BangPatterns #-}
 -- |
 -- The Haskell 2010 Prelude: a standard module imported by default
 -- into all Haskell modules.  For more documentation, see the Haskell 2010
 -- Report <http://www.haskell.org/onlinereport/>.
-
 module Prelude (
 
     -- * Standard types, classes and related functions

System/IO/Error.hs

+{-# OPTIONS_GHC -fno-warn-unused-imports #-}
+-- apparent bug in GHC, reports a bogus warning for the Prelude import below
 #if __GLASGOW_HASKELL__ >= 701
 {-# LANGUAGE Safe #-}
 #endif
 
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
--- apparent bug in GHC, reports a bogus warning for the Prelude import below
 module System.IO.Error (
       -- * I\/O errors
     IOError,                    -- = IOException