Another checkpoint.  More XXXes added...

Also add some labels to 2.6.rst and howto/unicode.rst so I can refer
to them.  (Somehow a label named 'module-contextlib' couldn't be
referenced -- why???)
diff --git a/Doc/howto/unicode.rst b/Doc/howto/unicode.rst
index 219bbfe..a01d723 100644
--- a/Doc/howto/unicode.rst
+++ b/Doc/howto/unicode.rst
@@ -1,3 +1,5 @@
+.. _unicode-howto:
+
 *****************
   Unicode HOWTO
 *****************