patch 9.0.0109: writing over the end of a buffer on stack

Problem:    Writing over the end of a buffer on stack when making list of
            spell suggestions.
Solution:   Make sure suggested word is not too long. (closes #10812)
diff --git a/src/testdir/test_spell_utf8.vim b/src/testdir/test_spell_utf8.vim
index 07cb87a..91ada1e 100644
--- a/src/testdir/test_spell_utf8.vim
+++ b/src/testdir/test_spell_utf8.vim
@@ -819,5 +819,13 @@
   bwipe!
 endfunc
 
+func Test_spell_suggest_too_long()
+  " this was creating a word longer than MAXWLEN
+  new
+  call setline(1, 'a' .. repeat("\u0333", 150))
+  norm! z=
+  bwipe!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab