Following up on r1553369, avoid an additional request at the end of every
revision sync in svnsync for atomic revprop change capable servers by passing
the revision of the just synced revision as old value.

* subversion/svnsync/svnsync.c
  (replay_baton_t): Add boolean.
  (replay_rev_finished): When the repository supports atomic revision property
    changes pass old value when the sync is done.
  (do_synchronize): Retrieve atomic revision property changes capability.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1553370 13f79535-47bb-0310-9956-ffa450edef68