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/floatobject.c b/Objects/floatobject.c
index efad212..4478168 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -1229,7 +1229,7 @@
 	 * exp+4*ndigits and exp-4*ndigits are within the range of a long.
 	 */
 
-	s = PyUnicode_AsStringAndSize(arg, &length);
+	s = _PyUnicode_AsStringAndSize(arg, &length);
 	if (s == NULL)
 		return NULL;
 	s_end = s + length;
@@ -1597,7 +1597,7 @@
 			     Py_TYPE(arg)->tp_name);
 		return NULL;
 	}
-	s = PyUnicode_AsString(arg);
+	s = _PyUnicode_AsString(arg);
 	if (s == NULL)
 		return NULL;
 	if (strcmp(s, "double") == 0) {