The assert is about binlogging must have been activated, but it was
not actually according to the reported how-to-repeat instuctions.
Analysis revealed that binlog_start_trans_and_stmt() was called
without prior testing if binlogging is ON.

Fixed with avoing entering binlog_start_trans_and_stmt() if binlog is
not activated.


mysql-test/r/skip_log_bin.result:
  new results.
mysql-test/t/skip_log_bin-master.opt:
  the option to deactivate binlogging.
mysql-test/t/skip_log_bin.test:
  regression test for the bug.
sql/sql_insert.cc:
  avoing entering binlog_start_trans_and_stmt() if binlog is not activated.