Tweak merge tests to reflect full "elidability" of empty rev range mergeinfo.
Tweak merge tests to reflect full "elidability" of empty rev range mergeinfo.

* subversion/tests/cmdline/merge_tests.py
  (empty_rev_range_mergeinfo): Merge info with nothing but empty revision
  ranges elides fully if the merge info overrides no other merge info or
  overrides merge info for a disjoint set of paths.  Also update test to
  expect new merge range notifications.

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