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/_sqlite/row.c b/Modules/_sqlite/row.c
index 008f19e..8778af0 100644
--- a/Modules/_sqlite/row.c
+++ b/Modules/_sqlite/row.c
@@ -82,12 +82,12 @@
         Py_XINCREF(item);
         return item;
     } else if (PyUnicode_Check(idx)) {
-        key = PyUnicode_AsString(idx);
+        key = _PyUnicode_AsString(idx);
 
         nitems = PyTuple_Size(self->description);
 
         for (i = 0; i < nitems; i++) {
-            compare_key = PyUnicode_AsString(PyTuple_GET_ITEM(PyTuple_GET_ITEM(self->description, i), 0));
+            compare_key = _PyUnicode_AsString(PyTuple_GET_ITEM(PyTuple_GET_ITEM(self->description, i), 0));
             if (!compare_key) {
                 return NULL;
             }