Following up on r1569551, update the libsvn_client 'svn diff' code to create a
diff processor in one place and directly pass that to all the different diff
implementations.

Move handling of all arguments that are only used for tree transformations
to libsvn_client (and the deprecated apis).

* subversion/include/private/svn_client_private.h
  (includes): Add private/svn_diff_tree.h.

* subversion/include/private/svn_wc_private.h
  (svn_wc__get_diff_editor): Update argument type.

* subversion/libsvn_client/diff.c
  (diff_wc_wc): Update caller. Use anchor output argument.
  (diff_repos_repos): Update argument type. Switch argument order.
  (diff_repos_wc): Update caller.
  (do_diff): Create diff processor. Update caller.

  (diff_summarize_repos_wc,
   diff_summarize_wc_wc,
   do_diff_summarize): Update caller.

* subversion/libsvn_client/diff_local.c
  (svn_client__arbitrary_nodes_diff): Use diff processor argument. Pass anchor
    to interested callers.

* subversion/libsvn_wc/deprecated.c
  (svn_wc_get_diff_editor6): Update caller.

* subversion/libsvn_wc/diff_editor.c
  (make_edit_baton,
   svn_wc__get_diff_editor): Update argument type. Remove now unused arguments.

* subversion/libsvn_wc/diff_local.c
  (diff_baton): Remove unused variable.
  (svn_wc_diff6): Rename to...
  (svn_wc__diff7): ... this. Update argument type. Remove now unused arguments.
    Allow providing anchor as output argument.
  (svn_wc_diff6): Reimplement as new function wrapping svn_wc__diff7.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1569697 13f79535-47bb-0310-9956-ffa450edef68