fix two #if MYSQL_VERSION_ID > 100105

SEQ_READ_APPEND is for two threads (reader and writer)
simultaneously accessing the IO_CACHE

Pretend that CREATE TABLE and CREATE TEMPORARY TABLE are
two different commands internally. The user doesn't need
to know that they both are SQLCOM_CREATE_TABLE.

Same for DROP [TEMPORARY] TABLE

* keep all com_xxx constants together in struct system_status_var
* fix an outdated comment in sql_cmd.h
* fix an off-by-one bug in mysqld.cc

as a bonus that makes CREATE TEMPORARY TEMPORARY TABLE illegal

Old code worked because plugin locking guaranteed that
encryption plugin is deinitialized last.
But compiled-in plugins are never locked.

This fixes encryption failures on fulltest builder

* support statically compiled file_key_management when possible
* rename encryption.encryption_create_or_replace -> encryption.create_or_replace
* delete unnecessary *.opt file (including
  have_key_management_plugin.inc is enough)
* remove unnecessary LOWER() for strings that are compared
  case insensitively anyway

Disable sys_vars.all_vars test. There's no need to write
boilerplate tests for every new system variable, our
INFORMATION_SCHEMA.SYSTEM_VARIABLES and sysvar_* tests
are now used to show all basic properties of all variables.

fix aes_decrypt of yassl to support zero-length input

Moving Item_func_spatial_rel from Item_bool_func to Item_bool_func2.
to make OP(const,field) use indexes.
- MBR functions supported OP(const,field) optimization in 10.0,
but were inintentionally broken in an earlier 10.1 change that introduced
a common parent for Item_func_spatial_mbr_rel and Item_func_spatial_precise_rel.
- Precise functions never supported optimization for OP(const,field).
Now both MBR and precise functions support OP(const,field) optimization.

any of the optimizer related functionality.

count_sargable_conds() instead for Item_func_in, Item_func_null_predicate,
Item_bool_func2. There other Item_int_func descendants that used to set
"sargable" to true (Item_func_between, Item_equal) already have their
own implementation of count_sargable_conds(). There is no sense to
have two parallel coding models for the same thing.

adding a separte class Item_func_spatial_relate for ST_RELATE().
This is a preparatory patch for:
 MDEV-8239 Reverse spatial operations OP(const, field) do not get optimized

Change session only variable enforce_storage_engine to be
session variable and make sure that also global value
is used if session variable is not set.

Item_func_eq's created during conversion of a ROW equality to a conjunction
of scalar equalities did not set cmp_context for its arguments properly,
so some of these created Item_func_eq could be later erroneously eliminated.

MDEV-8373 Zero date can be inserted in strict no-zero mode through CREATE TABLE AS SELECT timestamp_field

don't return NULL-s anymore, and actually they're not BOOLEAN.
Fixed.

The --gtid-ignore-duplicates option was not working correctly with row-based
replication. When a row event was completed, but before committing, there
was a small window where another multi-source SQL thread could wrongly try
to re-execute the same transaction, without properly ignoring the duplicate
GTID. This would lead to duplicate key error or out-of-order GTID error or
similar.

Thanks to Matt Neth for reporting this and giving an easy way to reproduce
the issue.

Introduce a new dummy INFORMATION_SCHEMA.CHANGED_PAGE_BITMAPS table to XtraDB
with reset_table callback to allow FLUSH NO_WRITE_TO_BINLOG CHANGED_PAGE_BITMAPS
to be called from innobackupex.

        The behaviour required by the standard seems too weird to expect.

This is an addition to original patch: cleanups for next_breadth_first_tab().

Overhead change:
next_breadth_first_tab()  0.04% -> out of radar

Split first_breadth_first_tab() into
JOIN::first_breadth_first_optimization_tab() and
JOIN::first_breadth_first_execution_tab().

This allows to eliminate function call and one condition. Adjusted callers
accordingly.

Overhead change:
first_breadth_first_tab()        0.07% -> out of radar
next_breadth_first_tab()         0.04% -> 0.04%
JOIN::cleanup()                  0.15% -> 0.11%
JOIN::save_explain_data_intern() 0.28% -> 0.24%

Moved Apc_target::destroy(), Apc_target::enable() and Apc_targe::disable()
definitions to my_apc.h so that they can be inlined.

Apc_targe::disable() now calls Apc_target::process_apc_requests() only if
there're APC requests. This saves one pthread_mutex_lock() call.

Overhead change:
Apc_target::disable              0.04% -> out of radar
Apc_target::enable               0.03% -> out of radar
Apc_target::process_apc_requests 0.02% -> out of radar
pthread_mutex_lock               0.43% -> 0.42%
pthread_mutex_unlock             0.26% -> 0.25%

        Some cases of the feature's borders were treated incorrectly.

The crash was caused by attempting to use a hashtable without
it getting initialized, due to the --skip-grant-tables switch.