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/Modules/cjkcodecs/cjkcodecs.h b/Modules/cjkcodecs/cjkcodecs.h
index 89c644c..0530a33 100644
--- a/Modules/cjkcodecs/cjkcodecs.h
+++ b/Modules/cjkcodecs/cjkcodecs.h
@@ -266,7 +266,7 @@
 				"encoding name must be a string.");
 		return NULL;
 	}
-	enc = PyUnicode_AsString(encoding);
+	enc = _PyUnicode_AsString(encoding);
 	if (enc == NULL)
 		return NULL;