Add a versionchanged directive to document addition of the new 'namereplace' error handler.

Reported by Robert on docs@p.o.
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index cd55099..89b2ac6 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1074,6 +1074,8 @@
       exception, the function now retries the system call instead of raising an
       :exc:`InterruptedError` exception (see :pep:`475` for the rationale).
 
+   .. versionchanged:: 3.5
+      The ``'namereplace'`` error handler was added.
 
 .. function:: ord(c)