patch 8.2.4247: stack corruption when looking for spell suggestions

Problem:    Stack corruption when looking for spell suggestions.
Solution:   Prevent the depth increased too much.  Add a five second time
            limit to finding suggestions.
diff --git a/src/testdir/test_spell.vim b/src/testdir/test_spell.vim
index 3c32450..a5c990a 100644
--- a/src/testdir/test_spell.vim
+++ b/src/testdir/test_spell.vim
@@ -773,6 +773,14 @@
   set nospell
 endfunc
 
+func Test_spellsuggest_too_deep()
+  " This was incrementing "depth" over MAXWLEN.
+  new
+  norm s000G00ý000000000000
+  sil norm ..vzG................vvzG0     v z=
+  bwipe!
+endfunc
+
 func LoadAffAndDic(aff_contents, dic_contents)
   set enc=latin1
   set spellfile=