queues.c cleanup and refactoring.

Restore old version of _downhead() (from before cd483c55)
that works well in an average case. Use it for queue_fix().

Move existing specialized version of _downhead() to queue_replace()
where it'll be handling the case it was specifically optimized for
(moving the element to the end of the queue).
And correct it to fix the heap not only down, but also up
(this fixes BUG#30301356).

Add unit tests.

Collateral cosmetic fixes.

CONCAT_WS didn't have it

DESCRIPTION:
============
There can be issues if the packets sent by the server
are not proper. Certain checks should be performed at the
client side while unpacking fields data.

FIX:
====
Check for the appropriate fields data and error out if it
is not present.

RB: 23601

The event scheduler has a THD which is used for e.g. keeping track
of the timing of the events. Thus, each scheduling of an event will
make use of this THD, which in turn allocates memory in the THD's
mem root. However, the mem root was never cleared, and hence, the
memory occupied would monotonically increase throughout the life
time of the server.

The root cause was found by Jon Olav Hauglid, and this fix clears the
THD's mem root for each event being scheduled.

Change-Id: I462d2b9fd9658c9f33ab5080f7cd0e0ea28382df

in fact, in MariaDB it cannot, but it can show spurious slaves
in SHOW SLAVE HOSTS.

slave was registered in COM_REGISTER_SLAVE and un-registered after
COM_BINLOG_DUMP. If there was no COM_BINLOG_DUMP, it would never
unregister.

Fix mtr error:

Bareword "HAVE_WIN32_CONSOLE" not allowed while "strict subs" in use at mysql-test-run.pl line 387.
Execution of mysql-test-run.pl aborted due to compilation errors.

Added in e3f5789a

Also fix the link to unicode.org repo, it is now on github.

Port this functionality from to Windows.
It requires Win32::Console module, which is already included into
Strawberry perl

test case

Cause:
In case of version based condtional comments, if the condition evaluates
to false, it is converted to a regular comment for replication by
replacing "!"  by " ".

Nested comment in a conditional comment is replicated as is. Nested
comments are supported only in case of conditional comments and when a
the comment on slave is no more a conditional comment, the statement
execution fails on the slave.

Fix:
Convert the nested comment, start from "/*" to "(*" and comment end from
"*/" to "*)" for replication.

Change-Id: I1a8e385a267b2370529eade094f0258fa96886c0

Several MYSQL_SYSVAR_STR parameters that employ both a validate
function callback fail to copy the string for saving the
validated value. The affected variables include the following:

innodb_ft_aux_table
innodb_ft_server_stopword_table
innodb_ft_user_stopword_table
innodb_buffer_pool_filename

The test case is an enhanced version of
mysql/mysql-server@0b0c30641fd66336e87394ac28587e40864f8af9
and the code changes are inspired by their fixes.

We are also importing and adjusting the test innodb_fts.stopword
to get coverage for the variable innodb_ft_user_stopword_table.

buf_dump(), buf_load(): Protect srv_buf_dump_filename with
LOCK_global_system_variables.

fts_load_user_stopword(): Minor cleanup

fts_load_stopword(): Remove the parameter global_stopword_table.

innobase_fts_load_stopword(): Protect innodb_server_stopword_table
against concurrent SET GLOBAL.

innodb_buffer_pool_evict_uncompressed(): Restart the loop when
prev_block might not enjoy mutex protection.

This is based on
mysql/mysql-server@eccaecac070b6747ecf14d6b9150791f8c3e8f6d

The only change is a change of the version number.
As noted in commit 02af6278
there were no changes to InnoDB between MySQL 5.6.46 and 5.6.47
either.

The function wsrep_on() was being called rather frequently
in InnoDB and XtraDB. Let us cache it in trx_t and invoke
trx_t::is_wsrep() instead.

innobase_trx_init(): Cache trx->wsrep = wsrep_on(thd).

ha_innobase::write_row(): Replace many repeated calls to current_thd,
and test the cheapest condition first.

fix embedded innodb_plugin tests

followup for 7198c6ab

Backport INSALL_SYMLINK cmake macro from 10.3.
It'll make libmysqlclient_r.* symlinks to link to the actual
shared library file, not to another symlink.

As a bonus it'll fix cmake warning about deprecated LOCATION property

This is a backport of the applicable part of
commit 93475aff and
commit 2c39f69d
from 10.4.

Before 10.4 and Galera 4, WSREP_ON is a macro that points to
a global Boolean variable, so it is not that expensive to
evaluate, but we will add an unlikely() hint around it.

WSREP_ON_NEW: Remove. This macro was introduced in
commit c863159c
when reverting WSREP_ON to its previous definition.

We replace some use of WSREP_ON with WSREP(thd), like it was done
in 93475aff. Note: the macro
WSREP() in 10.1 is equivalent to WSREP_NNULL() in 10.4.

Item_func_rand::seed_random(): Avoid invoking current_thd
when WSREP is not enabled.

_ma_fetch_keypage(): Correct an assertion that used to always hold.
Thanks to clang -Wint-in-bool-context for flagging this.

double_to_datetime_with_warn(): Suppress -Wimplicit-int-float-conversion
by adding a cast. LONGLONG_MAX converted to double will actually be
LONGLONG_MAX+1.

Since commit 7198c6ab
the ./mtr --embedded tests would fail to start innodb_plugin
because of an undefined reference to the symbol wsrep_log().

Let us define a stub for that function. The embedded server
is never built WITH_WSREP, but there are no separate storage
engine builds for the embedded server. Hence, by default,
the dynamic InnoDB storage engine plugin would be built WITH_WSREP
and it would fail to load into the embedded server library due to
a reference to the undefined symbol.

The name was correctly encoded in UTF-8 before
commit 0ce12f70.

In case of ipv6 not enabled tests like `main.ipv6, rpl.rpl_ipv6` failed on
aarch buildbot.
Fix it by following commits 70dcb46e and 0bae1957 for
`10.2`.

The first patch for the bug was erroneous: it did not take into account
the fact that the modified function get_key_scans_params() was called in
different contexts. As a result the patch caused a regression bug MDEV-22191.
The patch for this bug introduced an extra parameter. Actually we can
do without this parameter and use the fourth parameter for the same
puropose - to differentiate between the calls of the function for range
access and for index merge access.

Also removed the call of get_key_scans_params() in the code of the function
merge_same_index_scans() as not needed.

maria_page_crc_check_index(): Do not attempt to convert
HA_ERR_WRONG_CRC (176) to my_bool (char).
On platforms where char is signed, the 176 will be converted to -80.

It turns out that the callers only care whether the result is zero.
Let us return 1 in this case, like we do in all other error cases.

Several tests that involve stored procedures fail on 10.4 kvm-asan
(clang 10) due to stack overrun. The main contributor to this stack
overrun is mysql_execute_command(), which is invoked recursively
during stored procedure execution.

Rebuilding with cmake -DWITH_WSREP=OFF shrunk the stack frame size
of mysql_execute_command() by more than 10 kilobytes in a
WITH_ASAN=ON, CMAKE_BUILD_TYPE=Debug build. The culprit
turned out to be the macro WSREP_LOG, which is allocating a
separate 1KiB buffer for every occurrence.

We replace the macro with a function, so that the stack will be
allocated only when the function is actually invoked. In this way,
no stack space will be wasted by default (when WSREP and Galera
are disabled).

This backports commit b6c5657e
from MariaDB 10.3.1.

Without ASAN, compilers can be smarter and optimize the stack usage.
The original commit message mentions that 1KiB was saved on GCC 5.4,
and 4KiB on Mac OS X Lion, which presumably uses a clang-based compiler.

This PR fixes wrong size argument passed in `strncmp(arg, "--parent-pid", 10)` as the `"--parent-pid"` string has length of 12.

Closes #1502