patch 8.2.2415: no way to check for the cmdwin feature

Problem:    No way to check for the cmdwin feature, cmdline_hist is now always
            enabled.
Solution:   Add has('cmdwin') support. Skip arglist test on Windows
            temporarily.
diff --git a/src/testdir/test_tabpage.vim b/src/testdir/test_tabpage.vim
index 38a6283..dac6d80 100644
--- a/src/testdir/test_tabpage.vim
+++ b/src/testdir/test_tabpage.vim
@@ -617,6 +617,8 @@
 
 " Test for closing the tab page from a command window
 func Test_tabpage_close_cmdwin()
+  CheckFeature cmdwin
+
   tabnew
   call feedkeys("q/:tabclose\<CR>\<Esc>", 'xt')
   call assert_equal(2, tabpagenr('$'))