move the C sources to the subfolder pgf again for backwards compatibility

src/runtime/haskell/PGF2.hsc

@@ -41,7 +41,7 @@ import Data.Typeable
 import qualified Data.Map as Map
 import Data.IORef
 
-#include <pgf.h>
+#include <pgf/pgf.h>
 
 type AbsName  = String -- ^ Name of abstract syntax
 type ConcName = String -- ^ Name of concrete syntax

src/runtime/haskell/PGF2/FFI.hsc

@@ -9,7 +9,7 @@ import Foreign.Ptr
 import Foreign.ForeignPtr
 import qualified Data.Map as Map
 
-#include <pgf.h>
+#include <pgf/pgf.h>
 
 -- | An abstract data type representing multilingual grammar
 -- in Portable Grammar Format.

src/runtime/haskell/pgf2.cabal

@@ -25,7 +25,6 @@ library
 
   extra-libraries:     pgf
   cc-options:          -std=c99
-  c-sources:           utils.c
 
 test-suite basic
   type:       exitcode-stdio-1.0