MDEV-7692 MariaDB - mysql-test - SUITE:percona - percona.innodb_sys_index 'xtradb' fails - @@version_comment

The test checked version_comment which is not helpful, and it would
cause the mismatch on any build apart from default source builds.
Fixed by removing the check

1) fix 5.5.42 vs 5.5.41 problem, nested links;
2) fix older MariaDB vs MySQL problem, var_auto_** dirs were not
   removed from the tmpfs location.
Both problems were caused by vardir being expanded to real path
too early, in two different places in the script code

otherwise innodb plugin might invoke xtradb function with the same name,
and that might crash (./mtr --emb innodb.strict_mode)

update test results after the fix

safe_process puts its children (mysqld, in this case) into a separate
process group, to be able to kill it all at once.

buildslave kills mtr's process group when it loses connection to
the master.

result? buildslave kills mtr and safe_process, but leaves stale
mysqld processes in their own process groups.

fix: put safe_process itself into a separate process group, then
buildslave won't kill it and safe_process will kill mysqld'd
and itself when it will notice that the parent mtr no longer exists.

Analysis: after a red-black-tree lookup we use node withouth
checking did lookup succeed or not. This lead to situation
where NULL-pointer was used.

Fix: Add additional check that found node from red-back-tree
is valid.

Analysis: On master when executing (single/multi) row INSERTs/REPLACEs
InnoDB fallback to old style autoinc locks (table locks)
only if another transaction has already acquired the AUTOINC lock.
Instead on slave as we are executing log_events and sql_command
is not correctly set, InnoDB does not use new style autoinc
locks when it could.

Fix: Use new style autoinc locks also when
thd_sql_command(user_thd) == SQLCOM_END i.e. this is RBR event.

This bug manifests due to wrong computation and evaluation of
keyinfo->key_length. The issues were:
* Using table->file->max_key_length() as an absolute value that must not be
  reached for a key, while it represents the maximum number of bytes
  possible for a table key.
* Incorrectly computing the keyinfo->key_length size during
  KEY_PART_INFO creation. The metadata information regarding the key
  such the field length (for strings) was added twice.

When the binlog was rotated due to @@max_binlog_size, the values of the
binlog_shapshot_file and binlog_snapshot_position were inconsistent in case of
non-transactional DML. The position was refering to the old file, while the
filename was of the new file after rotation. This patch makes them consistent
by making sure the position is also refering to the new file.

Start the client API for low-level protocol access:
* unsigned long mysql_net_read_packet(MYSQL *mysql);
* unsigned long mysql_net_field_length(unsigned char **packet);

* fix /etc/init.d/mysql to use log-basename for pid-filename
* fix mysqld_safe not to force logging-to-file when log-basename is specified

include oqgraph into deb packages conditionally, just like we do with tokudb

Do not use merge_for_insert for commands which use SELECT because optimizer can't work with such tables.

Fixes which makes multi-delete working with normally merged views.

    When the distance in ST_BUFFER is too far negative the coordinates can run out of the operational
    area. We should just return an empty geometry in this case.

The testcase fails randomly due to ibuf merge happening in the background.
Fix not to do any merges with ibuf_debug enabled.

Previously IF NOT EXISTS was added in Debian version in revno 3543. 
Now added the same for Ubuntu.

MDEV-7435 Windows debug: Run-Time Check Failure #3 - The variable 'unused' is being used without being initialized.
Fixed as it's done in 10.0.

causes server crash

Analysis: If wrong data types used on foreign constraint there
was possibility that foreign->id is NULL when incorrect
foreign constraint was removed from the dictionary cache.

Fix: Add guard foreign->id != NULL before trying to lookup
or remove the foreign constraint from dictionary cache.

Tested using user database where problem was repeatable.

MDEV-7055: MySQL#74664 - InnoDB: Failing assertion: len <= col->len || col->mtype == 5 || (col->len == 0 && col->mtype == 1) in file rem0rec.cc line 845

Debug assertion maybe too strict.

Analysis: Purge thread does not have thd and no access to
handlerton.

Fix: If thd does not exists we use sql_print_warning instead
of push_warning_printf.

added a script to regenerate certificates easily in the future (2035!)
restored server8k-key.pem to actually be 8K key, as it was supposed to

Backport from mysql 5.7. The patch reviewed, test added.