Drop support for ghc-6.4 era OPTIONS pragmas

It's still possible to build with ghc-6.4 but you have to pass
extra flags like "ghc --make -cpp -fffi Setup.hs" We could not
keep those OPTIONS pragmas and make it warning-free with ghc-6.10.
See http://hackage.haskell.org/trac/ghc/ticket/2800 for details.

Distribution/Simple/InstallDirs.hs

-{-# OPTIONS -cpp -fffi #-}
--- OPTIONS required for ghc-6.4.x compat, and must appear first
 {-# LANGUAGE CPP, ForeignFunctionInterface #-}
-{-# OPTIONS_GHC -cpp -fffi #-}
 {-# OPTIONS_NHC98 -cpp #-}
 {-# OPTIONS_JHC -fcpp -fffi #-}
 -----------------------------------------------------------------------------

Distribution/Simple/Utils.hs

-{-# OPTIONS -cpp -fffi #-}
--- OPTIONS required for ghc-6.4.x compat, and must appear first
 {-# LANGUAGE CPP, ForeignFunctionInterface #-}
-{-# OPTIONS_GHC -cpp -fffi #-}
 {-# OPTIONS_NHC98 -cpp #-}
 {-# OPTIONS_JHC -fcpp -fffi #-}
 -----------------------------------------------------------------------------