Optionally include C run-time support

If the C run-time library is compiled and installed on your system, you can now
do 'cabal configure -fc-runtime' to get the following extras:
  + The haskell binding to the C run-time library will be included in the
    PGF library (so you can import it in Haskell applications).
    Documentation on the new modules will be included when you run
    'cabal haddock'.
  + The new command 'pgf-shell', implemented on top of haskell binding to
    the C run-time system.
  + Three new commands in the web API: c-parse, c-linearize and
    c-translate. Their interfaces are similar to the corresponding commands
    without the "c-" prefix, but they should be considered preliminary.

src/runtime/haskell-bind/CRuntimeFFI.hsc

@@ -15,8 +15,8 @@ module CRuntimeFFI(-- * PGF
                    ) where
 
 import Prelude hiding (fromEnum)
-import Control.Monad
-import System.IO
+--import Control.Monad
+--import System.IO
 import System.IO.Unsafe
 import CId (CId(..), 
             mkCId, wildCId,
@@ -26,11 +26,11 @@ import PgfLow
 
 import Foreign hiding ( Pool, newPool, unsafePerformIO )
 import Foreign.C
-import Foreign.C.String
-import Foreign.Ptr
+--import Foreign.C.String
+--import Foreign.Ptr
 
 
-import Data.Char
+--import Data.Char
 import qualified Data.ByteString as BS
 import Data.IORef