Rename PyUnicode_AsString -> _PyUnicode_AsString and
PyUnicode_AsStringAndSize -> _PyUnicode_AsStringAndSize to mark
them for interpreter internal use only.

We'll have to rework these APIs or create new ones for the
purpose of accessing the UTF-8 representation of Unicode objects
for 3.1.
diff --git a/Include/object.h b/Include/object.h
index 07a4b2c..f5ec7d4 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -466,7 +466,7 @@
 PyAPI_FUNC(long) _Py_HashPointer(void*);
 
 /* Helper for passing objects to printf and the like */
-#define PyObject_REPR(obj) PyUnicode_AsString(PyObject_Repr(obj))
+#define PyObject_REPR(obj) _PyUnicode_AsString(PyObject_Repr(obj))
 
 /* Flag bits for printing: */
 #define Py_PRINT_RAW	1	/* No string quotes etc. */