Privatize some editor-v2-only APIs.

* subversion/include/svn_delta.h
  (svn_delta_fetch_props_func_t, svn_delta_fetch_kind_func_t,
   svn_delta_fetch_base_func_t, svn_delta_shim_callbacks_t,
   svn_delta_shim_callbacks_default): Temporarily (until post-1.8)
    move these from here...

* subversion/include/private/svn_editor.h
  (svn_delta_fetch_props_func_t, svn_delta_fetch_kind_func_t,
   svn_delta_fetch_base_func_t, svn_delta_shim_callbacks_t,
   svn_delta_shim_callbacks_default): ...to here.

* subversion/include/svn_ra_svn.h,
* subversion/libsvn_client/client.h,
* subversion/libsvn_ra_serf/ra_serf.h
  Now also include "private/svn_editor.h".

Suggested by: rhuijben


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1459815 13f79535-47bb-0310-9956-ffa450edef68