On the fsx-id branch:  Remove most references to svn_fs_x__id_copy_id
such that it can be removed in the next commit.

* subversion/libsvn_fs_x/dag.h
  (svn_fs_x__dag_same_line_of_history): New DAG node comparison function.

* subversion/libsvn_fs_x/dag.c
  (svn_fs_x__dag_same_line_of_history): Implement directly accessing the
                                        noderev's copy ID.
  (make_entry): Directly access the parent noderev's copy ID.

* subversion/libsvn_fs_x/tree.c
  (compare_dir_structure): Call the new function instead of implementing
                           the logic locally.
  (merge): Same, plus update function call.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx-id@1646670 13f79535-47bb-0310-9956-ffa450edef68