Implementation of mysql_multi_update did not call multi_update::send_error method in some cases 
(see the test reported on bug page and test cases in changeset).

Fixed with deploying the method, ::send_error() is refined to get binlogging code which works whenever 
there is modified non-transactional table.
thd->no_trans_update.stmt flag is set in to TRUE to ease testing though being the beginning of relative 
bug#27417 fix (addresses a part of those issues).
Eliminating two minor issues (small bugs) in multi_update methods.
This patch for multi-update also addresses a part of the issues reported in bug#13270,bug#23333.