Switch svn_repos_open2() and svn_fs_open() to result/scratch pool paradigm.

* subversion/include/svn_fs.h
  (svn_fs_open2): Revv svn_fs_open() with SCRATCH_POOL argument.
  (svn_fs_open): Deprecate.

* subversion/include/svn_repos.h
  (svn_repos_open3): Revv svn_repos_open2() with SCRATCH_POOL argument.
  (svn_repos_open2): Implement deprecated function.

* subversion/libsvn_fs/fs-loader.c
  (fs_library_vtable): Remove subpool.
  (svn_fs_open2): Revv. Use SCRATCH_POOL for temporary allocations.
  (svn_fs_open): Implement deprecated function.

* subversion/libsvn_repos/deprecated.c
  (svn_repos_open2): Implement deprecated function.

* subversion/libsvn_repos/repos.c
  (get_repos): Add SCRATCH_POOL argument. Use it where appropriate.
  (svn_repos_open3): Revv svn_repos_open2(). Use SCRATCH_POOL for 
   temporary allocations.
  (svn_repos_upgrade2, svn_repos_recover4, multi_freeze, 
   svn_repos_db_logfiles, svn_repos_hotcopy2): Adapt callers of get_repos().

* subversion/mod_dav_svn/repos.c
  (get_resource): Use svn_repos_open3() with r->pool as SCRATCH_POOL.

* subversion/mod_dav_svn/version.c
  (cleanup_deltify): Use svn_repos_open3().

* subversion/svnserve/serve.c
  (find_repos): Add SCRATCH_POOL and use svn_repos_open3().
  (construct_server_baton): Update caller.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1589048 13f79535-47bb-0310-9956-ffa450edef68