patch 8.2.3512: timestamp test fails on some systems

Problem:    Timestamp test fails on some systems.
Solution:   Sleep for a short while.

src/testdir/test_stat.vim

@@ -103,6 +103,7 @@ func Test_autoread_fast()
 
   w!
   silent !echo bar > Xautoread
+  sleep 10m
   checktime
 
   call assert_equal('bar', trim(getline(1)))

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3512,
 /**/
     3511,
 /**/