On the fsx-id branch:  Simplify the noderevs container structure before
changing its ID representation.

* subversion/libsvn_fs_x/noderevs.c
  (svn_fs_x__noderevs_t): Have a common sub-container for all reps, text
                          and props alike.
  (svn_fs_x__noderevs_create,
   svn_fs_x__noderevs_add,
   svn_fs_x__noderevs_estimate_size,
   svn_fs_x__noderevs_get,
   svn_fs_x__write_noderevs_container,
   svn_fs_x__read_noderevs_container,
   svn_fs_x__serialize_noderevs_container,
   svn_fs_x__noderevs_get_func): Update all reps sub-container access.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx-id@1646678 13f79535-47bb-0310-9956-ffa450edef68