MDEV-10763: Wrong result - server does not return NULL values from default list partition after ALTER table

Fixed partition pruning for NULL value.

MDEV-10765: Wrong result - query does not retrieve values from default partition on a table partitioned by list columns

Partial matches should be treat as not exact one.

Conflicts:
	sql/mysqld.cc
	sql/slave.cc

When a deadlock kill is detected inside the storage engine, the kill
is not done immediately, to avoid calling back into the storage engine
kill_query method with various lock subsystem mutexes held. Instead the
kill is queued and done later by a slave background thread.

This patch in preparation for fixing TokuDB optimistic parallel
replication, as well as for removing locking hacks in InnoDB/XtraDB in
10.2.

Signed-off-by: Kristian Nielsen <knielsen at knielsen-hq.org>

DEFAULT partition support added to LIST and LIST COLUMN partitioning.
Partitions Prunning added for DEFAULT partititon.

Make the new (CTE-related) code in set_explain_type to take into
account that some JOIN_TABs are non-merged semi-joins, and do not
have a TABLE object.

MDEV-10758 engines/funcs.db_alter_collate_ascii and engines/funcs.db_alter_collate_utf8 fail with wrong results

Add a testcase

Add the testcase

This is the final patch removing some old remainders that are
not needed anymore.

(Other clean-ups were done in earlier commits)

does not work in non-debug modes.

The bug manifested itself for recursive definitions that
used anchors over tables with blobs.

without preceding sys_vars.wsrep_provider_basic

        mysql_prepare_create_table fixed so it doesn't let duplicating
        constraint names. Syntax for CONSTRAINT IF NOT EXISTS added
        and handled in mysql_alter_table.

Based on the patch from Daniil Medvedev (a Google Summer of Code task)

This bug in st_select_lex_node::move_node could result
in invalid select lists in recursive units that could
cause falling into infinite loops when iterating over
selects in such units.

take into account that the list of equal items in
an Item_equal object may contain items with type() == REF_ITEM.

The rdiff file needed to be adjusted after changes made in scope of MDEV-9864

for materialized views and derived tables: there were no
push-down if the view was defined as union of selects
without aggregation. Added test cases with such unions.

Adjusted result files after the merge of the code for mdev-9197.

Ability to print lock type added.
Restoring correct lock type for CREATE VIEW added.

Modifying innodb_ctype_ldml.test related files to take into account
the previous commit changes.