On the fsx-id branch:  Where immediately possible, replace access to the
noderev's full ID with access to the respective ID part.

* subversion/libsvn_fs_x/cached_data.c
  (get_dir_contents,
   locate_dir_cache, 
   svn_fs_x__get_proplist): Access the noderev_id part directly.

* subversion/libsvn_fs_x/dag.c
  (svn_fs_x__dag_get_node_id,
   svn_fs_x__dag_get_copy_id): Access the ID parts directly instead of
                               contructing a temp. svn_fs_t instance.

* subversion/libsvn_fs_x/fs_x.c
  (svn_fs_x__prop_rep_equal): Checking the noderev IDs is the correct
                              identity check for noderevs. Duh!

* subversion/libsvn_fs_x/low_level.c
  (svn_fs_x__read_noderev,
   svn_fs_x__write_noderev): No detour via the full ID required anymore.

* subversion/libsvn_fs_x/pack.c
  (copy_node_to_temp): The wanted ID parts are now readily available.

* subversion/libsvn_fs_x/transaction.c
  (create_new_txn_noderev_from_rev,
   svn_fs_x__set_entry,
   shards_spanned): Same.
  (rep_write_cleanup,
   rep_write_get_baton,
   rep_write_contents_close): Extract the txn ID directly from the
                              noderev_id.
  (set_representation): The noderev_id is enough to check for txns.
                        Store the correct ID (part) in an error message.
  (svn_fs_x__create_successor): The revision can now be read directly
                                from the noderev_id.
  (svn_fs_x__set_proplist): The noderev_id is now readily available.
  (write_final_rev): Remove redundant copying.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx-id@1645974 13f79535-47bb-0310-9956-ffa450edef68