patch 8.2.3867: implementation of some list functions too complicated

Problem:    Implementation of some list functions too complicated.
Solution:   Refactor do_sort_uniq(), f_count() and extend() (Yegappan
            Lakshmanan, closes #9378)
diff --git a/src/version.c b/src/version.c
index 2c46608..aa699a2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -750,6 +750,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3867,
+/**/
     3866,
 /**/
     3865,