patch 8.1.1353: undo test fails on Mac

Problem:    Undo test fails on Mac.
Solution:   Expect "private" on the Mac.

Author: brammool

src/testdir/test_undo.vim

@@ -442,7 +442,11 @@ funct Test_undofile()
 
   if isdirectory('/tmp')
     set undodir=/tmp
-    call assert_equal('/tmp/%tmp%file', undofile('///tmp/file'))
+    if has('osx')
+      call assert_equal('/tmp/%private%tmp%file', undofile('///tmp/file'))
+    else
+      call assert_equal('/tmp/%tmp%file', undofile('///tmp/file'))
+    endif
   endif
 
   set undodir&

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1353,
 /**/
     1352,
 /**/