Revert "base: Move CString, CStringLen to GHC.Foreign"

This reverts commit 5ec22f01.

libraries/base/Foreign/C/String.hs

@@ -110,11 +110,20 @@ import GHC.Base
 
 import {-# SOURCE #-} GHC.IO.Encoding
 import qualified GHC.Foreign as GHC
-import GHC.Foreign (CString, CStringLen)
 
 -----------------------------------------------------------------------------
 -- Strings
 
+-- representation of strings in C
+-- ------------------------------
+
+-- | A C string is a reference to an array of C characters terminated by NUL.
+type CString    = Ptr CChar
+
+-- | A string with explicit length information in bytes instead of a
+-- terminating NUL (allowing NUL characters in the middle of the string).
+type CStringLen = (Ptr CChar, Int)
+
 -- exported functions
 -- ------------------
 --

libraries/base/GHC/Foreign.hs

@@ -19,7 +19,6 @@
 
 module GHC.Foreign (
     -- * C strings with a configurable encoding
-    CString, CStringLen,
 
     -- conversion of C strings into Haskell strings
     --
@@ -75,11 +74,8 @@ putDebugMsg | c_DEBUG_DUMP = debugLn
             | otherwise    = const (return ())
 
 
--- | A C string is a reference to an array of C characters terminated by NUL.
+-- These definitions are identical to those in Foreign.C.String, but copied in here to avoid a cycle:
 type CString    = Ptr CChar
-
--- | A string with explicit length information in bytes instead of a
--- terminating NUL (allowing NUL characters in the middle of the string).
 type CStringLen = (Ptr CChar, Int)
 
 -- exported functions