Use __builtin_ctzll on GCC/Clang and _BitScanForward/_BitScanForward64 on
MSVC to speed up Table_map_iterator::next_bit(), up to 3 times in benchmarks

Removed Field_map, since it was used only in a single function.

Fixed is_indexed_agg_distinct(), since it relied on initialization of
Bitmap in constructor.

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)

- Do not scan registry to check if TCPIP is supported.
- Do not read registry under HKEY_LOCAL_MACHINE\SOFTWARE\MySQL anymore.
- Do not load threadpool function dynamically, it is available
since Win7.
- simplify win32_init_tcp_ip(), and return error of WSAStartup() fails.
- Correct comment in my_parameter_handler()

No need to do dynamic loading and fallbacks anymore.
We can safely assume Windows 7, and availability of all SRWLock functions.

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.