Revision 1905662

On the 'pristines-on-demand-on-mwf' branch: Expose the working copy text-base
sync function as a new public svn_wc API.

* subversion/include/private/svn_wc_private.h
  (svn_wc__textbase_fetch_cb_t, svn_wc__textbase_sync): Promote these
   private members …

* subversion/include/svn_wc.h
  (svn_wc_textbase_fetch_cb_t, svn_wc_textbase_sync): …into these new APIs.

* subversion/libsvn_client/textbase.c
  (): Adjust includes.
  (textbase_fetch_cb, svn_client__textbase_sync): Use the new public API.

* subversion/libsvn_wc/textbase.c
  (svn_wc__textbase_sync): Rename to …
  (svn_wc_textbase_sync): …this.  Adjust the type of `fetch_callback`.
  (textbase_sync_baton_t): Adjust the type of `fetch_callback`.