Simplify svnserve object pool usage:  Since we can't reuse open
repository instances ATM, drop the repository pool.  Instead make
the repository an object with connection lifetime (still created
lazily).

* subversion/svnserve/server.h
  (serve_params_t): Replace repos pool with the config hash that
                    we will need to open any repos directly.

* subversion/svnserve/svnserve.c
  (sub_main): FS_CONFIG is now part of the PARAMS struct and we
              don't have a REPOS_POOL anymore.

* subversion/svnserve/serve.c
  (reset_repos): We don't temporarily release repositories anymore,
                 thus we can drop this pool cleanup callback.
  (find_repos): Replace the REPOS_POOL with a FS_CONFIG hash such
                that we may call svn_repos_open2() directly.  Also,
                all return objects have the same lifetime now, hence
                only one pool is required.
  (construct_server_baton): Update caller. Be sure to give repository-
                            related objects the same lifetime as the
                            connection.
  (reopen_repos): No longer used.
  (serve_interruptable): No re-initialization of connections required
                         anymore.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1581923 13f79535-47bb-0310-9956-ffa450edef68