On the authzperf branch: Avoid double definition of svn_authz_t.
(Follow-up from broken r1613422)

* subversion/libsvn_repos/repos.h
  (svn_authz_t): Define here.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/authzperf@1613424 13f79535-47bb-0310-9956-ffa450edef68