patch 8.2.3512: timestamp test fails on some systems

Problem:    Timestamp test fails on some systems.
Solution:   Sleep for a short while.
diff --git a/src/version.c b/src/version.c
index f4e9f9f..691af12 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3512,
+/**/
     3511,
 /**/
     3510,