fill_alter_table() always thought that index was changed because of
of a wrong check of block_size. Some engines had code to correct this
that should not be needed, Aria didn't and because of this some online
operations didn't work.

This code fixes the comparision of block_size to only compare if it's set.

Currently trx_sys.mutex protects only trx_sys.mysql_trx_list and
trx_sys.m_views, which are not accessed by lock0lock debug routines.
Thus there's no need to bother trx_sys.mutex here.

Removed trx_assert_started(): this assertion is fully covered by
check_trx_state().

recv_sys_t::mutex and rw_trx_hash_elementi_t::mutex were acquired
in reverse (to recorded) order.

Fixed by releasing recv_sys_t::mutex, before iterating rw_trx_hash.
Statistics gathering doesn't really need recv_sys_t::mutex protection,
since it is always done in one thread (trx_roll_crash_recv_trx) and
thus it can't go wrong.

This is fixup after commit 8026cd62.
We must not silently allow a lock wait to occur during InnoDB data
dictionary transactions. The dict_operation_lock is supposed to
prevent lock waits, and we want to be aware of any errors.

Implementing the task according to the description.
Additionally, implementing Item_func_date_format::check_arguments().

Main changes:

- Changing the constructor to accept a CHARSET_INFO pointer, instead of an Item pointer
- Updating the bison grammar accordingly

Additional cleanups:

- Simplifying Item_func_set_collation::eq() by reusing Item_func::eq()
- Removing unused binary_keyword

Problem:
=======
	During validation of missing tablespace, missing tablespace id is
being compared with hash table of redo logs (recv_sys->addr_hash). But if the
hash table ran out of memory then there is a possibility that it will not contain
the redo logs of all tablespace. In that case, Server will load the InnoDB
even though there is a missing tablespace.

Solution:
========
	If the recv_sys->addr_hash hash table ran out of memory then InnoDB needs
to scan the remaining redo log again to validate the missing tablespace.

The problem resided in this branch of the "option_value_no_option_type" rule:

| '@' '@' opt_var_ident_type internal_variable_name equal set_expr_or_default

Summary:

1. internal_variable_name initialized tmp.var to trg_new_row_fake_var (0x01).
2. The condition "if (tmp.var == NULL)" did not check
   the special case with trg_new_row_fake_var,
   so Lex->set_system_variable(&tmp, $3, $6) was
   called with tmp.var pointing to trg_new_row_fake_var,
   which created a sys_var instance pointing to 0x01 instead of
   a real system variable.
3. Later, at the trigger invocation time, this method was called:
   sys_var::do_deprecated_warning (this=0x1, thd=0x7ffe6c000a98)
   Notice, "this" is equal to trg_new_row_fake_var (0x01)

Solution:

The old implementation with separate rules
internal_variable_name (in sql_yacc.yy and sql_yacc_ora.yy) and
internal_variable_name_directly_assignable (in sql_yacc_ora.yy only)
was too complex and hard to follow.

Rewriting the code in a more straightforward way.

1. Changing LEX::set_system_variable()

from:

bool set_system_variable(struct sys_var_with_base *, enum_var_type, Item *);

to:

bool set_system_variable(enum_var_type, sys_var *, const LEX_CSTRING *, Item *);

2. Adding new methods in LEX, which operate with variable names:

bool set_trigger_field(const LEX_CSTRING *, const LEX_CSTRING *, Item *);
bool set_system_variable(enum_var_type var_type, const LEX_CSTRING *name,
                         Item *val);
bool set_system_variable(THD *thd, enum_var_type var_type,
                         const LEX_CSTRING *name1,
                         const LEX_CSTRING *name2,
                         Item *val);
bool set_default_system_variable(enum_var_type var_type,
                                 const LEX_CSTRING *name,
                                 Item *val);
bool set_variable(const LEX_CSTRING *name, Item *item);

3. Changing the grammar to call the new methods directly
   in option_value_no_option_type,
   Removing rules internal_variable_name and
   internal_variable_name_directly_assignable.

4. Removing "struct sys_var_with_base" and trg_new_row_fake_var.

Good side effect:

- The code in /sql reduced from 314 to 183 lines.
- MDEV-15615 Unexpected syntax error instead of "Unknown system variable" ...
  was also fixed automatically

When the plugin is unloaded, walk the s_trx_list and delete the left over
Rdb_transaction objects.
It is responsibility of the SQL layer to make sure that the storage engine
has no open tables when the plugin is being unloaded.

Scientific notation handling fixed.

Conflicts:
	mysql-test/r/func_json.result
	mysql-test/t/func_json.test

Scientific notation handling fixed.

and remove redundant have_innodb.inc, it's included in
galera_cluster.inc anyway.

and remove redundant have_innodb.inc, it's included in
galera_cluster.inc anyway.

extra/mariabackup/ds_buffer.c:145:9: warning: pointer targets in assignment differ in signedness [-Wpointer-sign]

information can be obtained.

plugin only enabled for Linux, as it fails building on BSD/MacOSX.
disks.test fixed.

information can be obtained.

disks.test moved to plugin's directory.

Changed "local" datasink logic to detect page compressed Innodb tables.

Whenever such table is detected, holes in the copied files are created by
skipping over binary zeros at the end of each compressed page.

             time and don't let server shut down

Queries from I_S in "Filling schema table" state didn't check killed
flag. For large tables this phase may take a while to complete.

Fixed by adding thd->killed flag check for each processed row.

MDEV-15570 Assertion `Item_cache_temporal::field_type() != MYSQL_TYPE_TIME' failed in Item_cache_temporal::val_datetime_packed

remove an assert. TIME value can be used (and cached) in a datetime context

galera SST tests have a debug part, but we don't want to limit them
to fulltest2 builder. So, add support for test files that
have a debug part:

* add maybe_debug.inc and maybe_debug.combinations
* 'debug' combination is run when debug is available
* 'release' combination is run otherwise
* test wraps debug parts in if($with_debug) { ... }
* and creates ,debug.rdiff for debug results

create galera.galera_sst_mariabackup

* make galera.galera_sst_xtrabackup* not big
* auto-select between socat and nc, whatever available
* auto-skip xtrabackup tests if no xtrabackup or neither socat nor nc

make galera.galera_sst_rsync not big