Expand merge_tests.py to cover issues 2823 and 2839.
Expand merge_tests.py to cover issues 2823 and 2839.

* subversion/tests/cmdline/merge_tests.py
  (merge_to_path_with_switched_children): Expand test to expect
  non-inheritable mergeinfo revision ranges in accordance with the
  functional spec.  Add comment that XFail is temporary until issues 2823
  and 2839 are fixed.
  (test_list): Temporarily set merge_to_path_with_switched_children as XFail
  to prevent needless breakage reports from the buildbots.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion