patch 9.0.0492: cmdwin test fails on MS-Windows

Problem:    Cmdwin test fails on MS-Windows.
Solution:   Skip test on MS-Windows.
diff --git a/src/testdir/test_cmdwin.vim b/src/testdir/test_cmdwin.vim
index fe849bc..8066831 100644
--- a/src/testdir/test_cmdwin.vim
+++ b/src/testdir/test_cmdwin.vim
@@ -380,6 +380,9 @@
 
 " This was using a pointer to a freed buffer
 func Test_cmdwin_freed_buffer_ptr()
+  " this does not work on MS-Windows because renaming an open file fails
+  CheckNotMSWindows
+
   au BufEnter * next 0| file 
   edit 0
   silent! norm q/