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/Objects/object.c b/Objects/object.c
index ff16994..79f8288 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -856,7 +856,7 @@
 	if (tp->tp_getattro != NULL)
 		return (*tp->tp_getattro)(v, name);
 	if (tp->tp_getattr != NULL)
-		return (*tp->tp_getattr)(v, PyUnicode_AsString(name));
+		return (*tp->tp_getattr)(v, _PyUnicode_AsString(name));
 	PyErr_Format(PyExc_AttributeError,
 		     "'%.50s' object has no attribute '%U'",
 		     tp->tp_name, name);
@@ -896,7 +896,7 @@
 		return err;
 	}
 	if (tp->tp_setattr != NULL) {
-		err = (*tp->tp_setattr)(v, PyUnicode_AsString(name), value);
+		err = (*tp->tp_setattr)(v, _PyUnicode_AsString(name), value);
 		Py_DECREF(name);
 		return err;
 	}
@@ -1062,7 +1062,7 @@
 
 	PyErr_Format(PyExc_AttributeError,
 		     "'%.50s' object has no attribute '%.400s'",
-		     tp->tp_name, PyUnicode_AsString(name));
+		     tp->tp_name, _PyUnicode_AsString(name));
   done:
 	Py_DECREF(name);
 	return res;