patch 8.0.0411: menu translations don't match when case is changed.

Problem:    We can't change the case in menu entries, it breaks translations.
Solution:   Ignore case when looking up a menu translation.
diff --git a/src/testdir/test_menu.vim b/src/testdir/test_menu.vim
index be55946..8fdaa1f 100644
--- a/src/testdir/test_menu.vim
+++ b/src/testdir/test_menu.vim
@@ -1,9 +1,29 @@
 " Test that the system menu can be loaded.
 
+if !has('menu')
+  finish
+endif
+
 func Test_load_menu()
   try
     source $VIMRUNTIME/menu.vim
   catch
     call assert_false(1, 'error while loading menus: ' . v:exception)
   endtry
+  source $VIMRUNTIME/delmenu.vim
+endfunc
+
+func Test_translate_menu()
+  if !has('multi_lang')
+    return
+  endif
+  if !filereadable($VIMRUNTIME . '/lang/menu_de_de.latin1.vim')
+    throw 'Skipped: translated menu not found'
+  endif
+
+  set langmenu=de_de
+  source $VIMRUNTIME/menu.vim
+  call assert_match(':browse tabnew', execute(':menu File.In\ neuem\ Tab\ öffnen\.\.\.'))
+
+  source $VIMRUNTIME/delmenu.vim
 endfunc