patch 8.1.0544: setting 'filetype' in a modeline causes an error

Problem:    Setting 'filetype' in a modeline causes an error (Hirohito
            Higashi).
Solution:   Don't add the P_INSECURE flag when setting 'filetype' from a
            modeline.  Also for 'syntax'.
diff --git a/src/testdir/test_modeline.vim b/src/testdir/test_modeline.vim
index 3bde58d..c1eb991 100644
--- a/src/testdir/test_modeline.vim
+++ b/src/testdir/test_modeline.vim
@@ -6,7 +6,83 @@
   let modeline = &modeline
   set modeline
   call assert_fails('split Xmodeline', 'E518:')
+
   let &modeline = modeline
   bwipe!
   call delete('Xmodeline')
 endfunc
+
+func Test_modeline_filetype()
+  call writefile(['vim: set ft=c :', 'nothing'], 'Xmodeline_filetype')
+  let modeline = &modeline
+  set modeline
+  filetype plugin on
+  split Xmodeline_filetype
+  call assert_equal("c", &filetype)
+  call assert_equal(1, b:did_ftplugin)
+  call assert_equal("ccomplete#Complete", &ofu)
+
+  bwipe!
+  call delete('Xmodeline_filetype')
+  let &modeline = modeline
+  filetype plugin off
+endfunc
+
+func Test_modeline_syntax()
+  call writefile(['vim: set syn=c :', 'nothing'], 'Xmodeline_syntax')
+  let modeline = &modeline
+  set modeline
+  syntax enable
+  split Xmodeline_syntax
+  call assert_equal("c", &syntax)
+  call assert_equal("c", b:current_syntax)
+
+  bwipe!
+  call delete('Xmodeline_syntax')
+  let &modeline = modeline
+  syntax off
+endfunc
+
+func Test_modeline_keymap()
+  call writefile(['vim: set keymap=greek :', 'nothing'], 'Xmodeline_keymap')
+  let modeline = &modeline
+  set modeline
+  split Xmodeline_keymap
+  call assert_equal("greek", &keymap)
+  call assert_match('greek\|grk', b:keymap_name)
+
+  bwipe!
+  call delete('Xmodeline_keymap')
+  let &modeline = modeline
+  set keymap= iminsert=0 imsearch=-1
+endfunc
+
+func s:modeline_fails(what, text)
+  let fname = "Xmodeline_fails_" . a:what
+  call writefile(['vim: set ' . a:text . ' :', 'nothing'], fname)
+  let modeline = &modeline
+  set modeline
+  filetype plugin on
+  syntax enable
+  call assert_fails('split ' . fname, 'E474:')
+  call assert_equal("", &filetype)
+  call assert_equal("", &syntax)
+
+  bwipe!
+  call delete(fname)
+  let &modeline = modeline
+  filetype plugin off
+  syntax off
+endfunc
+
+func Test_modeline_filetype_fails()
+  call s:modeline_fails('filetype', 'ft=evil$CMD')
+endfunc
+
+func Test_modeline_syntax_fails()
+  call s:modeline_fails('syntax', 'syn=evil$CMD')
+endfunc
+
+func Test_modeline_keymap_fails()
+  call s:modeline_fails('keymap', 'keymap=evil$CMD')
+endfunc