patch 8.0.0444: diffpatch fails when the file name has a quote

Problem:    Diffpatch fails when the file name has a quote.
Solution:   Escape the name properly. (zetzei)
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index c23e8a1..e09bcaa 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -319,7 +319,7 @@
   new
   call assert_fails('diffpatch Xpatch', 'E816:')
 
-  for name in ['Xpatch', 'Xpatch$HOME']
+  for name in ['Xpatch', 'Xpatch$HOME', 'Xpa''tch']
     call setline(1, ['1', '2', '3'])
     if name != 'Xpatch'
       call rename('Xpatch', name)