patch 8.2.3659: integer overflow with large line number

Problem:    Integer overflow with large line number.
Solution:   Check for overflow. (closes #9202)
diff --git a/src/testdir/test_normal.vim b/src/testdir/test_normal.vim
index e17aca4..732456d 100644
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -3519,4 +3519,25 @@
   bw!
 endfunc
 
+func Test_normal_count_out_of_range()
+  new
+  call setline(1, 'text')
+  normal 44444444444|
+  call assert_equal(999999999, v:count)
+  normal 444444444444|
+  call assert_equal(999999999, v:count)
+  normal 4444444444444|
+  call assert_equal(999999999, v:count)
+  normal 4444444444444444444|
+  call assert_equal(999999999, v:count)
+
+  normal 9y99999999|
+  call assert_equal(899999991, v:count)
+  normal 10y99999999|
+  call assert_equal(999999999, v:count)
+  normal 44444444444y44444444444|
+  call assert_equal(999999999, v:count)
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab