On the authzperf branch:  Make /**/ segments match empty paths, i.e. zero
segments, as well.  That is in line with what e.g. zsh globbing does as well.

We must start applying var-segment nodes together with their parents instead
of applying them only with the next segment.  To make the code simplier,
normalize sequences of multiple var-segment wildcards to single var-segment.
This eliminates the need to enumerate them recursively.

* subversion/libsvn_repos/authz.h
  (authz_rule_segment_t): Update the docstring about the "**" pattern.

* subversion/libsvn_repos/authz_parse.c
  (parse_rule_path):  Modify normalization code, swallowing successive 
                      "any recursive" segments.

* subversion/libsvn_repos/authz.c
  (init_lockup_state,
   add_next_node): Add var-segment nodes to the result along with their
                   parents. 
  (lookup): Var-segment nodes have already been added.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/authzperf@1621387 13f79535-47bb-0310-9956-ffa450edef68