Original problem reported by Wlad: re-compilation of 10.3 on top of 10.2
build would cache undefined HAVE_ISINF from 10.2, whereas it is expected
to be 1 in 10.3.

std::isinf() seem to be available on all supported platforms.

Being executed under slow_log is ON the test revealed a "side-effect"
in MDEV-8305 implementation which inadvertently made the trigger or
stored function statements to reset the top-level query's
THD::start_time et al. (Details of the test failure analysis are footnoted).
Unlike the SP case the SF and Trigger's internal statement should not
do that.

Fixed with revising the MDEV-8305 decision to backup/reset/restore
the session timestamp inside sp_instr_stmt::execute(). The timestamp
actually remains reset in the SP case by its caller per statement basis by ever
existing logics.

Timestamps related tests are extended to cover the trigger and stored function case.

Note, commit 3395ab73 is reverted as its struct QUERY_START_TIME_INFO
declaration is not in use anymore after this patch.

Footnote:
--------
Specifically to the failing test, a query on the master was logged
okay with a timestamp of the query's top-level statement but its post
update trigger managed to compute one more (later) timestamp which got
inserted into another table. The latter table master-vs-slave
no fractional part timestamp discrepancy became evident
thanks to different execution time of the trigger combined with the
fact of the logged with micro-second fractional part master timestamp
was truncated on the slave. On master when the fractional part was
close to 1 the trigger execution added up its own latency to overflow
to next second value. That's how the master timestamp surprisingly
turned out to bigger than the slave's one.

Add libzstd-dev as a build dependency to the server and libzstd1 as a
runtime dependency for rocksdb. libzstd is practially a mandatory
compression library to ensure adequate performance for RocksDB.

thd_destructor_proxy(): Ensure that purge actually exits,
like the logic should have been ever since MDEV-14080.

srv_purge_shutdown(): A new function to wait for the
purge coordinator to exit. Before exiting, the
purge coordinator will ensure that all purge workers have exited.

This is the MariaDB 10.2 version of the patch.

field_store_string(): Simplify the code.

field_store_index_name(): Remove, and use field_store_string()
instead. Starting with MariaDB 10.2.2, there is the predicate
dict_index_t::is_committed(), and dict_index_t::name never
contains the magic byte 0xff.

Correct some comments to refer to TEMP_INDEX_PREFIX_STR.

i_s_cmp_per_index_fill_low(): Use the appropriate value NULL to
identify that an index was not found. Check that storing each
column value succeeded.

i_s_innodb_buffer_page_fill(), i_s_innodb_buf_page_lru_fill():
Only invoke Field::set_notnull() if the index was found.
(This fixes the bug.)

i_s_dict_fill_sys_indexes(): Adjust the index->name that was
directly loaded from SYS_INDEXES.NAME (which can start with
the 0xff byte). This was the only function that depended
on the translation in field_store_index_name().

The list was created based on 10.2.15 list, with the addition
of failures and modifications which happened during the last week
before the tentative 10.3.7 release commit

This is addition to parent revision fixing build failures.

finite is not used anymore in code base. isfinite is part of C99 and we
assume we only support compilers that support C99.

Fix an obvious typo: replace_column should be applied to SHOW TABLE STATUS,
not to SELECT * FROM t1.

1. Adding LEX::make_item_sysvar() and reusing it
   in sql_yacc.yy and sql_yacc_ora.yy.
   Removing the "opt_component" rule.

2. Renaming rules to better reflect their purpose:
   - keyword to keyword_ident
   - keyword_sp to keyword_label
   - keyword_sp_not_data_type to keyword_sp_var_and_label

   Also renaming:
   - sp_decl_ident_keyword to keyword_sp_decl for naming consistency
   - keyword_alias to keyword_table_alias,
     for consistency with ident_table_alias
   - keyword_sp_data_type to keyword_data_type,
     as it has nothing SP-specific.

3. Moving GLOBAL_SYM, LOCAL_SYM, SESSION_SYM from
   keyword_sp_var_and_label to a separate rule keyword_sysvar_type.
   We don't have system variables with these names anyway.
   Adding ident_sysvar_name and using it in the grammar that needs
   a system variable name instead of ident_or_text.
   This removed a number of shift/reduce conflicts
   between GLOBAL_SYM/LOCAL_SYM/SESSION_SYM as a variable scope and
   as a variable name.

4. Moving keywords BEGIN_SYM, END (in both *.yy fiels)
   and EXCEPTION_SYM (in sql_yacc_ora.yy) into a separate
   rule keyword_sp_block_section, because in Oracle verb keywords
   (COMMIT, DO, HANDLER, OPEN, REPAIR, ROLLBACK, SAVEPOINT, SHUTDOWN, TRUNCATE)
   are good variables names and can appear in e.g. DECLARE,
   while block keywords (BEGIN, END, EXCEPTION) are not good variable names
   and cannot appear in DECLARE.

5. Further splitting keyword_directly_not_assignable in sql_yacc_ora.yy:
   moving keyword_sp_verb_clause out. Renaming the rest of
   keyword_directly_not_assignable to keyword_sp_head,
   which represents keywords that can appear in optional
   clauses in CREATE PROCEDURE/FUNCTION/TRIGGER.

6. Renaming keyword_sp_verb_clause to keyword_verb_clause,
   as now it does not contains anything SP-specific.

   As a result or #4,#5,#6, the rule keyword_directly_not_assignable
   was replaced to three separate rules:
   - keyword_sp_block
   - keyword_sp_head
   - keyword_verb_clause
   Adding the same rules in sql_yacc.yy, for unification.

6. Adding keyword_sp_head and keyword_verb_clause into keyword_sp_decl.
   This fixes MDEV-16244.

7. Reorganizing the rest of keyword related rules into two groups:
  a. Rules defining a list of keywords and consisting of only terminal symbols:
    - keyword_sp_var_not_label
    - keyword_sp_head
    - keyword_sp_verb_clause
    - keyword_sp_block_section
    - keyword_sysvar_type

  b. Rules that combine the above lists into keyword places:
    - keyword_table_alias
    - keyword_ident
    - keyword_label
    - keyword_sysvar_name
    - keyword_sp_decl
  Rules from the group "b" use on the right side only rules
  from the group "a" (with optional terminal symbols added).
  Rules from the group "b" DO NOT mutually use each other any more.
  This makes them easier to read (and see the difference between them).

  Sorting the right sides of the group "b" keyword rules alphabetically,
  for yet better readability.

Crash happened when deleting all columns that was part of a check constraint

The bug was that read map for from table was used when
checking CHECK constraint and was not properly reset
in copy_data_between_tables()

Step#1: RocksDB files require a special #define when they are compiled
with valgrind. Without that, valgrind fails with an 'unimplemented syscall'
error for fcntl call.

Fixed by marking NEXTVAL() and LASTVAL() to be replicated row based

In a test case Update occurs between Search and Delete/Update. This corrupts rowid
which Search saves for Delete/Update. Patch prevents this by using of
HA_EXTRA_REMEMBER_POS and HA_EXTRA_RESTORE_POS in a partition code.

This situation possibly occurs only with system versioning table and partition.
MyISAM and Aria engines are affected.

fix by midenok
Closes #705

Fixing PERIOD to PERIOD_SYM in the %left command.

The failures with valgrind occur as a result of Spider sometimes using the
wrong transaction for operations in background threads that send requests to
the data nodes.  The use of the wrong transaction caused the networking to the
data nodes to use the wrong thread in some cases.  Valgrind eventually
detects this when such a thread is destroyed before it is used to disconnect
from the data node by that wrong transaction when it is freed.

I have fixed the problem by correcting the transaction used in each of these
cases.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Merged:
  Commit 4d576d9d on branch bb-10.3-MDEV-12900

The failures with valgrind occur as a result of Spider sometimes using the
wrong transaction for operations in background threads that send requests to
the data nodes.  The use of the wrong transaction caused the networking to the
data nodes to use the wrong thread in some cases.  Valgrind eventually
detects this when such a thread is destroyed before it is used to disconnect
from the data node by that wrong transaction when it is freed.

I have fixed the problem by correcting the transaction used in each of these
cases.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

Merged:
  Commit 4d576d9d on branch bb-10.3-MDEV-12900

The failures with valgrind occur as a result of Spider sometimes using the
wrong transaction for operations in background threads that send requests to
the data nodes.  The use of the wrong transaction caused the networking to the
data nodes to use the wrong thread in some cases.  Valgrind eventually
detects this when such a thread is destroyed before it is used to disconnect
from the data node by that wrong transaction when it is freed.

I have fixed the problem by correcting the transaction used in each of these
cases.

Author:
  Jacob Mathew.

Reviewer:
  Kentoku Shiba.

- Using array_elements() instead of a constant to iterate through an array
- Adding some comments
- Adding new-line function comments
- Using STRING_WITH_LEN instead of C_STRING_WITH_LEN

- Removing the unused "THD*" paramer from Lex_ident_sys_st::to_size_number()
- Removing redundant #include for "sql_tvc.h" and "vers_utils.h"