- Initialize variables that could be used uninitialized
- Added extra end space to DbugStringItemTypeValue to get rid of warnings
  from c_ptr()
- Session_sysvars_tracker::update() accessed unitialized memory if called
  with NULL value.
- get_schema_stat_record() accessed unitialized memory if HA_KEY_LONG_HASH
  was used
- parse_vcol_defs() accessed random memory for tables without keys.

MDEV-19301 Assertion `!is_valid_datetime() || fraction_remainder(((item->decimals) < (6) ? (item->decimals) : (6))) == 0' failed in Datetime_truncation_not_needed::Datetime_truncation_not_needed

Ignore the setreuid() return here.

Make sure that the references in the GROUP BY clause that need to be considered for
pushdown from having to where are of Item_field objects

Use LOCK_server_started, COND_server_started and mysqld_server_started for waiting starting the server

Do not cast wrong type.

We use own IO callbacks from server code anyway.

Fix reinitialize vers_write on table reopen.

Make all accesses to btr_cur_n_non_sea atomic.

Use the same select as for usual table list (forgotten oracle mode parser fixed)

fix is simple: just move mp->file under mp->global protection

MDEV-18350 Using audit plugin with MySQL, mysqld crashes when running COM_INIT_DB against invalid database.

mysql_event_general structure changed in 10.3.
the database_length should be size_t now instead of the int.

Turn off versioned_write for DELETE HISTORY.

* Made make_versioned_*() proxies inline;
* Renamed truncate_history to delete_history

Part of:
MDEV-19814 Server crash in row_upd_del_mark_clust_rec or Assertion
`update->n_fields < ulint(table->n_cols + table->n_v_cols)' failed in
upd_node_t::make_versioned_helper