bpo-39498 Start linking the security warnings in the stdlib modules (GH-18272)


Co-authored-by: Ɓukasz Langa <lukasz@langa.pl>
(cherry picked from commit c5c5326d4799fe4ae566aff32ed3461af95859cc)

Co-authored-by: Anthony Shaw <anthony.p.shaw@gmail.com>
diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index ae4f7bf..945ac42 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1187,6 +1187,7 @@
     >>> arr2
     array('i', [0, 1, 2, 3, 4, 0, 0, 0, 0, 0])
 
+.. _multiprocessing-recv-pickle-security:
 
 .. warning::