c99 style for assigning structure members

MDEV-7987 Fatal error: Please read "Security" section of the manual to find out how to run mysqld as root!

update the error message to refer to the knowledge base
that (now) has an article about this use case

        Fixed by using POINT instead of ST_POINT in the item.
        Later need to fix that with proper ST_POINT implementation

Fixed by reverting incorrect fix of MDEC-7055 (reopened) and removing the
test case (because it now crashes).

Fixed overflow error that caused fewer bites to be allocated than
necessary on Windows 64 bit. This is due to ulong being 32 bit on
64 bit Windows and 64 bit on 64 bit Linux.

on disconnect THD must clean user_var_events array before
dropping temporary tables. Otherwise when binlogging a DROP,
it'll access user_var_events, but they were allocated
in the already freed memroot.

take into account that argc can be 0
(if there were no commands on the command line)

Don't use a fixed buffer for X509_NAME_oneline() in the client.
Do as the server does - allocate it dynamically.

For a test - regenerate certificates to have the server cert with
a long subject.

MDEV-7585 Assertion `thd->is_error() || kill_errno || thd->killed == ABORT_QUERY' failed in ha_rows filesort

if we clear the error status (in THD::clear_error())
make sure to clear the thd->killed == KILL_BAD_DATA too,
because it was caused by the error that we're clearing.

Remove the too restrictive bugfix for bug#67088.
FIFO can be used for general/slow logs, but lseek() and fsync() on
FIFO fail. And open() needs to be non-blocking, in case the other
end isn't reading.

because current_thd is NULL and ER() causes sigsegv

The double call of ref used tables fixed.

MDEV-7126 replication slave - deadlock in terminate_slave_thread with stop slave and show variables of replication filters and show global status

Three-way deadlock:

  T1: SHOW GLOBAL STATUS
      -> acquire LOCK_status
  T2: STOP SLAVE
      -> acquire LOCK_active_mi
      -> terminate_slave_thread()
      -> -> cond_timedwait for handle_slave_sql to stop
  T3: sql slave thread (same applies to io thread)
      -> handle_slave_sql(), when exiting
      -> -> THD::add_status_to_global()
      -> -> -> wait for LOCK_status...
  T1: SHOW GLOBAL STATUS
      -> for "Slave_heartbeat_period" status variable
      -> -> show_heartbeat_period()
      -> -> -> wait for LOCK_active_mi

cherry-pick from 5.6:

  commit fc8b395898f40387b3468122bd0dae31e29a6fde
  Author: Venkatesh Duggirala <venkatesh.duggirala@oracle.com>
  Date:   Wed Jun 12 21:41:05 2013 +0530

    BUG#16904035-SHOW STATUS - EXCESSIVE LOCKING ON LOCK_ACTIVE_MI AND
    ACTIVE_MI->RLI->DATA_LOCK

    Problem: Excessive locking on lock_active_mi and rli->data_lock
    while executing any `show status like 'X'` command.

    Analysis: SHOW_FUNCs for Slave_running, Slave_retried_transactions,
    Slave_heartbeat_period, Slave_received_heartbeats,
    Slave_last_heartbeat are acquiring lock_active_mi and rli->data_lock
    to show their variable value. It is ok to show stale data while showing
    the status variables i.e., even if they miss one update, it will
    not cause any great trouble.

    Fix: Remove the locks from the above mentioned SHOW_FUNC functions.

Add a test case

Merge pull request #39 from openquery/MDEV-7977-mutex-unlock_LOCK_log-in-MYSQL_BIN_LOG_write_incident

MDEV-7977 MYSQL_BIN_LOG::write_incident failing to release LOCK_log

Taking into account implicit dependence of constant view field from nullable table of left join added.

Fixed finding real table to check if it turned to NULL (materialized view & derived taken into account)

Removed incorrect uninitialization.

save_prep_leaf_tables() made recursive to work with underlying view

Arena restoiring fixed in case of EOM.

convert_subq_to_sj() must check the results of in_equality->fix_fields()
call. It can fail in a meaningful way when e.g. we're trying to compare
columns with incompatible collations.

Cherry-picking https://github.com/olesalscheider/server/commit/fc4df415049271ef625783c31f2999e7d1bdc816
(it was a 10.1 pull request, we want it in 5.5)

MDEV-7820 Server crashes in in my_strcasecmp_utf8 on subquery in ORDER B...

It is possible for Item_field to have a NULL field_name. This is true if
the Item_field is created based on a field in a temporary table that has
no name. It is thus necessary to do a null check before attempting a
strcmp.