Need to take into account cases of a polygon shaped as a very thin line.

The variables now return real values. They can't be made usual variables because they do not have DEFAULT value.

Problem was in reinitialization of first_successful_insert_id_in_prev_stmt_for_binlog after setting variables.

The problem is in the IsSimple function. If the first and the last points
of a curve coincide it's and exception and the line is still 'simple'.

Index names were not formatted correctly.

The 'srid' field's copying was missing in the copying Create_field::Create_field() constructor.

Merge from Percona Server enforced use of a specific storage engine
authored by Stewart Smith.

Modified to be session variable and modifiable only by SUPER. Use
similar implementation as default_storage_engine.

- Renaming Item::is_bool_func() to is_bool_type(), to avoid assumption
  that the item is an Item_func derivant.
- Deriving Item_func_spatial_rel from Item_bool_func rather than Item_int_func

fixed embedded server tests
MDEV-7009: SET STATEMENT min_examined_row_limit has no effect
MDEV-6948:SET STATEMENT gtid_domain_id = ... FOR has no effect (same for gtid_seq_no and server_id)

old values of SET STATENENT variables now saved in its own Query_arena and restored later

the problem was in assigning default value during parsing.

(changes of backported patch are very small: strlen removed, error processing fixed, view open statistics added)

Double error reporting removed.

* watch for "redefined macro" warning
* don't enable -D_FORTIFY_SOURCE=2 in debug builds (it requires -O)

common parent class for Item_func_isnull and Item_func_isnotnull

Add holder thread_id, file_name and line to output.

MDEV-7025 ANALYZE SELECT/INSERT/UPDATE/DELETE from a view does not check access permissions on the view

Added access checking for the ANALYZE statement command.

Fix Item_ident::print() to work when there is no current database

Change r_rows to be double

add forgotten initialization of the mutex name

disable a broken test, pending a proper fix

otherwise innodb plugin might invoke xtradb function with the same name,
and that might crash (./mtr --emb innodb.strict_mode)

update test results after the fix

safe_process puts its children (mysqld, in this case) into a separate
process group, to be able to kill it all at once.

buildslave kills mtr's process group when it loses connection to
the master.

result? buildslave kills mtr and safe_process, but leaves stale
mysqld processes in their own process groups.

fix: put safe_process itself into a separate process group, then
buildslave won't kill it and safe_process will kill mysqld'd
and itself when it will notice that the parent mtr no longer exists.

Analysis: after a red-black-tree lookup we use node withouth
checking did lookup succeed or not. This lead to situation
where NULL-pointer was used.

Fix: Add additional check that found node from red-back-tree
is valid.