Separate svn_client__get_diff_editor() in a function that takes diff callbacks
and one that takes the new svn_diff_tree_processor_t.

* subversion/include/private/svn_wc_private.h
  (svn_wc__wrap_diff_callbacks): Constify output argument and handle
     walk_deleted_dirs.

* subversion/libsvn_client/client.h
  (includes): Add svn_diff_tree.h.

* subversion/libsvn_client/diff.c
  (svn_client__get_diff_editor2): New function, intended to replace...
  (svn_client__get_diff_editor): ... this function, which is now a wrapper.

* subversion/libsvn_client/merge.c
  (notification_receiver): Remove function.
  (drive_merge_report_editor): Update caller.

* subversion/libsvn_client/repos_diff.c
  (edit_baton): Constify processor. Remove variable.
  (diff_deleted_dir): Only check skip_children for skipping deleted.

* subversion/libsvn_wc/diff_editor.c
  (diff_notify_baton_t): Remove unused variables.
  (diff_state_handle,
   diff_state_close): Remove functions.
  (diff_state_absent): Remove notification.
  (svn_client__get_diff_editor): Rename to ...
  (svn_client__get_diff_editor2): ... this and forward diff processor.
  (svn_client__get_diff_editor): New function around
     svn_client__get_diff_editor2, providing diff callbacks.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1440139 13f79535-47bb-0310-9956-ffa450edef68