On the fsfs-format7 branch: "flatten" one level of the fsfs ID data
structure by making the private ID an extension of the public ID.
No interface is affected by this change.  As we will eliminate the
the string elements from this structure in later commits, the end-
result is a flat structure that can be copied and compared easily.

This is part of the "numerical IDs" patch series.

* subversion/libsvn_fs_fs/id.c
  (id_private_t): replaced by ...
  (fs_fs__id_t): ... this one
  (svn_fs_fs__id_node_id,
   svn_fs_fs__id_copy_id,
   svn_fs_fs__id_txn_id,
   svn_fs_fs__id_rev,
   svn_fs_fs__id_item,
   svn_fs_fs__id_unparse,
   svn_fs_fs__id_eq,
   svn_fs_fs__id_check_related): cast types instead chasing pointers
  (svn_fs_fs__id_txn_create,
   svn_fs_fs__id_rev_create,
   svn_fs_fs__id_copy,
   svn_fs_fs__id_parse,
   svn_fs_fs__id_serialize,
   svn_fs_fs__id_deserialize): eliminate the "private struct" indirection


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1453595 13f79535-47bb-0310-9956-ffa450edef68