Stop using some deprecated functions.

* subversion/mod_dav_svn/util.c
  (get_last_history_rev): Use svn_fs_node_history2() and svn_fs_history_prev2()
    instead of their predecessors to silence deprecation warning.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1618589 13f79535-47bb-0310-9956-ffa450edef68