Add a system variable spider_slave_trx_isolation.
- spider_slave_trx_isolation
  The transaction isolation level when Spider table is used by slave SQL thread.
  -1 : OFF
   0 : READ UNCOMMITTED
   1 : READ COMMITTED
   2 : REPEATABLE READ
   3 : SERIALIZABLE
  The default value is -1

Miscellaneous Spider typos

Change default value of the followings
quick_mode 0 -> 3
quick_page_size 100 -> 1024

Add the following parameter for limiting result page size by byte
- quick_page_byte(qpb)
  Number of bytes in a page when acquisition one by one.
  When quick_mode is 1 or 2, Spider stores at least 1 record even if
  quick_page_byte is smaller than 1 record. When quick_mode is 3,
  quick_page_byte is used for judging using temporary table.
  That is given to priority when server parameter spider_quick_page_byte
  is set.
  The default value is 10485760

Fix "out of sync" issue at using quick_mode = 1 or 2

The fields of the temporary table were not created in create_tmp_table function. Because item->const_item() was true. But the temporary tables that is created by Spider are always used all columns. So Spider should call create_tmp_table function with TMP_TABLE_ALL_COLUMNS flag.

The parameters innodb_file_format and innodb_large_prefix were overridden
in the Debian-distributed configuration files, because the default values
of these parameters between MariaDB 5.5 and MariaDB 10.2
did not make any sense.

To allow a more seamless upgrade from MariaDB 10.1 to later versions,
let InnoDB recognize the parameters innodb_file_format and
innodb_large_prefix and issue deprecation warnings for them if they
are specified. A deprecation period of only one major release
(one year between the MariaDB 10.2 and 10.3 releases) is insufficient
for these widely used parameters.

and gitignore myrocks_hotbackup (as it's now generated)

Closes #1081

Closes #1080

It's too late. Might work or not (and on buster it doesn't).

MDEV-18057 Assertion `(node->state == 5) || (node->state == 6)' failed in row_upd_sec_step upon DELETE after UPDATE failed due to FK violation

The idea of the fix: reset state from previous query.

row_upd_clust_step(): reset cached index before updating a clustered index

Closes #1133

Remove fil_node_t::sync_event.

I had a discussion with kernel fellows and they said it's safe to call
fsync() simultaneously at least on VFS and ext4. So initially I wanted
to disable check for recent Linux but than I realized code is buggy.

Consider a case when one thread is inside fsync() and two others are
waiting inside os_event. First thread after fsync() calls os_event_set()
which is a broadcast! So two waiting threads will awake and may call
fsync() at the same time.

One fix is to add a notify_one() functionality to os_event but I decided
to remove incorrect check completely. Note, it works for one waiting
thread but not for more than one.

IMO it's ok to avoid existing bugs but there is not too much sense in
avoiding possible(!) bugs as this code does.

fil_space_t::is_in_rotation_list(), fil_space_t::is_in_unflushed_spaces():
Replace redundant bool fields with member functions.

fil_node_t::needs_flush: Replaces fil_node_t::modification_counter and
fil_node_t::flush_counter. We need to know whether there _are_ some
unflushed writes and we do not need to know _how many_ writes.

fil_system_t::modification_counter: Remove as not needed.
Even if we needed fil_node_t::modification_counter, every file
could have its own counter that would be incremented on each write.

fil_system_t::modification_counter is a global modification counter
for all files. It was incremented on every write. But whether some
file was flushed or not is an internal fil_node_t deal/state and
this makes fil_system_t::modification_counter useless.

Closes #1061

MDEV-18379: Unification of check for IPv6

Currently, the three-node mtr suite for Galera (galera_3nodes)
uses a separate IPv6 availability check using the "have_ipv6.inc"
file. This check duplicates a more accurate check at suite.pm
level, which can be used by including the file "check_ipv6.inc".

This patch removes this discrepancy between suites. In addition,
one of the files in the galera_3nodes suite does not contain the
option "--bind-address=::" which is needed for the test to work
correctly with IPv6 (at least on some systems), since without
it the server will not wait for connections on the IPv6 interface.

https://jira.mariadb.org/browse/MDEV-18379

Add a simplest regression test. Specifically, I want to be sure that
SYS_COLUMNS.LEN is increased.

Closes #1123

fix of incorrect 10.3 merge

MDEV-18372: Minor MDEV-17973-related merge issue to 10.3

Use the same data type 'ulong' to avoid type mismatch on Windows
and on 32-bit systems.

FIXME: The correct data type should probably be 64-bit.

When innobase_allocate_row_for_vcol() returns true (for failure),
it may already have invoked mem_heap_create(). However, some callers
would fail to invoke mem_heap_free().

pcre needs symbols from pcreposix
(but this is only an issue when linking with system static libraries)

Problem:
========
Server fails to notify the engine by not setting the ADD_PK_INDEX and
DROP_PK_INDEX When there is a
 i) Change in candidate for primary key.
 ii) New candidate for primary key.

Fix:
====
Server sets the ADD_PK_INDEX and DROP_PK_INDEX while doing alter for the
above problematic case.

I missed this in commit 9a7281a7

PROBLEM
-------

1. We are inserting a base column entry which causes an invalid value
   by the function provided to generate virtual column,but we go ahead
   and insert this due to ignore keyword.
2. We then delete this record, making this record delete marked in innodb.
   If we try to insert another record with the same pk as the deleted
   record and if the rec is not purged ,then we try to undelete mark this
   record and try to build a update vector with previous and updated value
   and while calculating the value of virtual column we get error from
   server that we cannot calculate this from base column.
   Innodb assumes that innobase_get_computed_value() Should always return
   a valid value for the base column present in the row. The failure of
   this call was not handled ,so we were crashing.

FIX

Thanks to commit 2614a0ab
before MDEV-5800, no version of MariaDB is affected by this bug
that was fixed in MySQL 5.7.25.

10.1 part: SHOW CREATE USER didn't show the password, if plugin was set,
but authentication_string was not

remove tests that rely on specific execution order

remove tests that rely on specific execution order