avoid some code duplication in url-transfer ftp methods * url-transfer.cc (url_transfer::ftp_file_or_dir_action): New function. (url_transfer::cwd, url_transfer::del, url_transfer::rmdir, url_transfer::mkdir): Call ftp_file_or_dir_action.

%!function r = f (x)
%!  if (ischar (x))
%!    r = x;
%!  else
%!    error ("expecting character string");
%!  endif
%!endfunction

%!assert (eval ("f 10;"), "10");