On the authzperf branch:  Fix segfault introduced in r1618875.
We perform prefix lookups using two different types of parameters,
segments during model construction, C strings during path lookup.

* subversion/libsvn_repos/authz.c
  (compare_segment): Rename to ...
  (compare_node_rule_segment): ... this.
  (compare_node_path_segment): New variant, re-instantiating
                               the pre-r1618875 code.
  (ensure_node_in_array,
   add_prefix_matches): Use the respective correct compare function.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/authzperf@1621358 13f79535-47bb-0310-9956-ffa450edef68