The warning out of OPTIMIZE
  Statement is unsafe because it uses a system function
was indeed counterfactual and was resulted by checking an
insufficiently strict property of lex' sql_command_flags.

Fixed with deploying an additional checking of weather
the current sql command that modifes a share->non_determinstic_insert
table is capable of generating ROW format events.
The extra check rules out the unsafety to OPTIMIZE et al, while the
existing check continues to do so to CREATE TABLE (which is
perculiarly tagged as ROW-event generative sql command).

As a side effect sql_sequence.binlog test gets corrected and
binlog_stm_unsafe_warning.test is reinforced to add up
an unsafe CREATE..SELECT test.