Code review comment for lp:~tsarev/percona-server/18580

- Please surround OPT_SLOW_QUERY_LOG_* in enum options_mysqld by #ifndef DBUG_OFF.
- I do not understand the descriptions
  "Replace X by value of variable in the Query_time: X in the slow query log."
  "When 0 (the default) use the actual value X. Used only for debugging."
  and
  "Replace X by value of variable in the Lock_time: X in the slow query log."
  "When 0 (the default) use the actual value X. Used only for debugging.",
  Please ping me on IRC to discuss them.
- Query_log_event::write: double semicolons ";;" at the end of lines.
- The test could have been simpler I think, with just a few representative cases, but this one is OK.