Add tests for 'svnrdump dump' and 'svnrdump load' with mergeinfo that refers
to r0. Part of issue #4476 "Mergeinfo containing r0 makes svnsync and dump
and load fail".

* subversion/tests/cmdline/svnrdump_tests_data/mergeinfo-contains-r0.dump,
  subversion/tests/cmdline/svnrdump_tests_data/mergeinfo-contains-r0.expected.dump
  New files, copied from svnsync_tests_data/ and updated to dump format 3.

* subversion/tests/cmdline/svnrdump_tests.py
  (dump_mergeinfo_contains_r0): New test, passing.
  (load_mergeinfo_contains_r0): New test, XFail.
  (test_list): Run them.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1646479 13f79535-47bb-0310-9956-ffa450edef68