On the authzperf branch: Prepare for state reuse between authz lookups.

This patch simply makes the lookup state per filtered_rules_t, i.e. per
user and repository because we can't share results between users.

* subversion/libsvn_repos/authz.c
  (filtered_rules_t): Move lookup_state here from ...
  (svn_authz_t): ... this one.
  (get_filtered_tree): Initialize the lookup state as well and return
                       the full filter struct instead of just the root. 
  (svn_repos__create_authz): Update.
  (svn_repos_authz_check_access): Update caller.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/authzperf@1615436 13f79535-47bb-0310-9956-ffa450edef68