Switch svnserve to use the new object pool structures.

So far, this simply saves some runtime and memory.  Future commits
will enable svnserve to serve large numbers connections with a
limited number of threads in a round-robin scheme.

* subversion/svnserve/server.h
  (repository_t): the parameters are now stored with the repos_pool
  (serve_params_t): for the same reason, we drop caching flags;
                    add global object pools / factories to used

* subversion/svnserve/serve.c
  (load_pwdb_config): read data through a configuration object pool
  (load_authz_config): read data through an authz object pool
  (find_repos): accept and use the object pools
  (serve): update caller

* subversion/svnserve/svnserve.c
  (main): adapt to changed parameter struct;
          instantiate the object pools;
          use them

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1541317 13f79535-47bb-0310-9956-ffa450edef68