MDEV-19585  Assertion with S3 table and flush_tables

The limit has to be increased so that MariaDB can create system tables.
It should not have any notable impact on performance.

There should not be any notable performance differences between 1K and 4K,
especially for temporary tables. In most cases using bigger blocks is also
faster (with the possible exception of doing key reads of not fixed length
keys).

The problem was two fault:
- flush_tables() wrongly gave errors when failing to open read only tables
- backup_block_ddl() didn't properly ignores errors from flush_tables()

The test case for this will be pushed in 10.5 as the test involves
S3 tables.

os0once.h: remove as not used now

zip_pad_info_t::mutex_created: remove along with corresponding stuff

zip_pad_info_t::mutex: make member value instead of a pointer

dict_table_t::stats_latch_created: remove along with related stuff

dict_table_t::stats_latch: make value member, not pointer. And always lock this
for simplicity, even to stats cloned table.

based on the work of Sergey Vojtovich

Get rid of os_once.

MDEV-19049 Server crashes in check_duplicate_long_entry_key, ASAN stack-buffer-overflow in Field_blob::get_key_image

Long Unique keys should always be last unique key.

Limit lines to ~16K

The bug occured when the optimizer decided to use a rowid filter built
by a range index scan to access an InnoDB table with generated clustered
index.
When a table is accessed by a secondary index Idx employing a rowid filter the
the value of pk contained in the found index tuple is checked against the
filter. A call of the handler function position is supposed to put the
pk value into the handler::ref buffer. However for generated clustered
primary keys it did not happened. The patch fixes this problem.

Make Field::is_equal() const and return bool as it's a naturally fitting
type for it. Also it's agrument was narrowed to Column_definition.

InnoDB can change type of some columns by itself. InnoDB-specific code used to
reside in Field_xxx:is_equal() methods. Now engine-specific stuff was
moved to a virtual methods of handler::can_convert{string,varstring,blob,geom}.
These methods are called by Field::can_be_converted_by_engine() which is a
double dispatch pattern.

Some InnoDB-specific code still resides in compare_keys_but_name(). It should
be moved from here someday to handler::compare_key_parts(...) or similar.

IS_EQUAL_WITH_REINTERPRET_COMPATIBLE_CHARSET
IS_EQUAL_WITH_REINTERPRET_COMPATIBLE_CHARSET_BUT_COLLATE: both was removed

IS_EQUAL_NO, IS_EQUAL_YES are not needed now and should be removed
along with deprecated handler::check_if_incompatible_data().

HA_EXTENDED_TYPES_CONVERSION: was removed as such logic is not needed now by
server code.

ALTER_COLUMN_EQUAL_PACK_LENGTH: was renamed to a more generic
ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE

Patch is about two cases:
1) On some collate changes it's possible to rebuild only secondary indexes
2) For non-indexed columns collate can be changed INSTANTly

Implemented mostly in Field_{string,varstring,blob}::is_equal().
Make this method return how exactly collationa differs.
This information is later used by fill_alter_inplace_info() to pass
correct info to engine.

Introduced the convert_to_printable_required_length to return the correct length(taking into
consideration of dots in the case of error messages).

The test cases for the MDEV found several independent bugs
in MariaDB server and Aria:
- If a temporary table was marked as crashed, it could never
  be deleted.
- Opening of a crashed temporary table gave an error message
  but the error was never forwarded to the caller which caused
  an assert() in my_ok()
- init_read_record() did mmap of all temporary tables, which is
  probably not a good idea as this area can potentially be
  very big. Changed code to only mmap internal temporary tables.
- mmap-ed tables where not unmapped in case of repair/optimize
  which caused bad data in table and crashes if the original
  table files where replaced with new ones (as the old mmap
  was still in place). Fixed by removing the mmap in case
  of repair.
- Cleaned up usage of code that disabled mmap in Aria

Problem was that in case of implicit rollback for alter table
Aria did try to run commit twice.

The test case for this is tricky to do in 10.2, so it will
be added to 10.4 as part of BACKUP STAGE testing.

MDEV-18832 Galera: 10.4 node crashed with Assertion `state() == s_committing' if you create SEQUENCE, use it, then drop and recreate and use again (#1339)

We could still end committing to binlog even in rollback.
Do not proceed with WSREP commit in this case.

MDEV-18940 Galera: Rolling upgrade: all nodes except upgraded node5 failed with Assertion `meta->gtid.seqno == wsrep_thd_trx_seqno(thd)' with SEQUENCEs (#1342)

Empty write sets will not trigger apply callback, and will not
update thread wsrep_trx_meta.gtid.seqno. Because of that assert will
be triggered when commit callback is called.

In collaboration with Sergey Vojtovich <svoj@mariadb.org>

The COMPRESSED clause is now a part of the data type and goes immediately
after the data type and length, but before the CHARACTER SET clause,
and before column attributes such as DEFAULT, COLLATE, ON UPDATE,
SYSTEM VERSIONING, engine specific column attributes.

In the old reduction, the COMPRESSED clause was a column attribute.

New syntax:
  <varchar or text data type> <length> <compression> <character set> <column attributes>
  <varbinary or blob data type> <length> <compression> <column attributes>

New syntax examples:
  VARCHAR(1000) COMPRESSED CHARACTER SET latin1 DEFAULT ''
  BLOB COMPRESSED DEFAULT ''

Deprecate syntax examples:
  VARCHAR(1000) CHARACTER SET latin1 COMPRESSED DEFAULT ''
  TEXT          CHARACTER SET latin1 DEFAULT '' COMPRESSED
  VARBINARY(1000) DEFAULT '' COMPRESSED

As a side effect:
- COMPRESSED is not valid as an SP label name in SQL/PSM routines any more
  (but it's still valid as an SP label name in sql_mode=ORACLE)

- COMPRESSED is now allowed in combination with GENERATED ALWAYS AS:

  TEXT COMPRESSED GENERATED ALWAYS AS REPEAT('a',1000)

followup for 0a43df4f

Do not check my_errno before it is set, check errno instead.
Also, do not check errno, if prior pread() did not fail.

Restore the detection of default charset in command line utilities.
It worked up to 10.1, but was broken by Connector/C.

Moved code for detection of default charset from sql-common/client.c
to mysys, and make command line utilities to use this code if charset
was not specified on the command line.

There was two separate problems:
- Aria pagecache didn't properly handle re-reading of blocks
  that have given errors before (this triggered an assert)
- temporary tables that where opened several times where
  not properly closed in ALTER, REPAIR or OPTIMIZE table

Other things
- Added a couple of asserts that will make it easier to
  find problems like this in the future.

post-merge fixes:
* .gitignore
* don't put the keyword COMPONENT into ${COMP} anymore
* don't alias mytop, but do alias mysql_client_test
* don't symlink manpages, use troff aliasing technique instead
  (symlinked manpages break rpm and out-of-source bintar builds)
* move debian to use troff aliased manpages, fix typos in debian files,
  put aliases in the correct packages, add more aliases to match
  rpm/bintar packaging

in HEAP btree indexes, the address of a record in memory is part of the
key. So, when inserting many identical keys, the actual btree
shape is defined by how and where records in memory are allocated.

records_in_range uses floats to estimate the size of the chunk of the
btree between min and max records, it depends on the btree shape and,
thus, is not portable either. As are optimizer decisions that are based
on records_in_range estimations, if the number happens to be close
to a tipping point.

as a fix, reduce the number of matching rows, so that even with
system-specific variations the optimizer would still pick the
expected plan.

Fixes heap.heap failure (range vs ALL) on ppc64

if ${CRC32_LIBRARY} target has no COMPILE_FLAGS yet,
GET_TARGET_PROPERTY returns COMPILE_FLAGS-NOTFOUND, which
doesn't work very well when it's later fed back into COMPILE_FLAGS.

GET_PROPERTY() returns an empty string in this case.

MDEV-15526 SysV init service deployed file '/etc/init.d/mysql' prevents systemctl disable command to work correctly (mariadb|mysql naming support) (debian/ubuntu)

mariadb service is controlled by systemd

Do not install SysV init script on Debian/Ubuntu in /etc/init.d/
put it in /usr/share/mysql in case the user would need it for something.

Use systemctl in pre/post scripts directly
without funky conditionals and wrapper scripts