Revision 1837289

Removed unused copyfrom-handling in RA-serf's update-editor code path.

[Reverted in r1837290 as it violates backward compatibility.]

No callers of svn_ra_do_update|switch() request 'send_copyfrom_args', and
the update-editor itself asserts that no copyfrom args are passed to it,
yet this RA-serf update-editor pass-though layer still contained code to
act on and pass through copyfrom args. This is now being removed.

A follow-up to r998193, "Finish issue #3711 by completing the purge of
copyfrom-args-over-update code from the client."

See https://issues.apache.org/jira/browse/SVN-3711, "Drop client support for
copyfrom-over-update".

* subversion/libsvn_ra_serf/update.c
  (dir_baton_t,
   file_baton_t,
   create_dir_baton,
   create_file_baton): Drop the copyfrom fields.
  (ensure_dir_opened,
   ensure_file_opened): Don't pretend to pass copyfrom args to the editor.
  (fetch_for_file): Don't attempt to select a delta base from copyfrom args.
  (update_opened): Don't attempt to receive copyfrom args from the server.
    Assert that none were transmitted.