Implement PEP 393.
diff --git a/Objects/stringlib/undef.h b/Objects/stringlib/undef.h
new file mode 100644
index 0000000..40b4391
--- /dev/null
+++ b/Objects/stringlib/undef.h
@@ -0,0 +1,10 @@
+#undef  FASTSEARCH
+#undef  STRINGLIB
+#undef  STRINGLIB_CHAR
+#undef  STRINGLIB_STR
+#undef  STRINGLIB_LEN
+#undef  STRINGLIB_NEW
+#undef  STRINGLIB_RESIZE
+#undef  _Py_InsertThousandsGrouping
+#undef  _Py_InsertThousandsGroupingLocale
+