On the fsfs-ucsnorm branch: update DAG API and documentation with the
changes needed to support normalized lookups.

[This is a checkpoint commit; the code does not compile.]

* subversion/libsvn_fs_fs/dag.c (dag_node_t):
   Document the semantics of the 'created_path' member.
* subversion/libsvn_fs_fs/dag.h
  (svn_fs_fs__dag_get_created_path): Likewise, for the return value.
  (svn_fs_fs__dag_open, svn_fs_fs__dag_dir_entry, svn_fs_fs__dag_clone_child,
   svn_fs_fs__dag_delete, svn_fs_fs__dag_make_dir, svn_fs_fs__dag_make_file):
   Rename parameter 'name' to 'key' and update documentaiton.
  (svn_fs_fs__dag_set_entry): Add parameter 'key' and update documentation.
  (svn_fs_fs__dag_copy): Add parameter 'key', rename 'entry' to 'name' and
   update documentation.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-ucsnorm@1563861 13f79535-47bb-0310-9956-ffa450edef68