The method subselect_union_engine::no_rows() must take
into account the fact that now unit->fake_select_lex is
NULL for for select_union_direct objects.

Although the original code of mysql-5.7 was adjusted
to the current MariaDB code the main ideas of the optimization
were preserved.

Add ANALYZE STMT handling into INSERT command.

remove:
* NDB from everywhere
* IM from mtr-v1
* packaging/rpm-oel and packaging/rpm-uln
* few unused spec files
* plug.in file
* .bzrignore

TOTAL_SSL_CONNECTIONS columns in CLIENT_STATISTICS and USER_STATISTICS

Extend existing plugins to support
* SHOW QUERY_RESPONSE_TIME
* FLUSH QUERY_RESPONSE_TIME
* SHOW LOCALE

move userstat tables to use the new API instead of
hand-coded syntax

INFORMATION_SCHEMA.SYSTEM_VARIABLES

1. @@boolean_var differs from SHOW VARIABLES
2. @@str_var ignored variable charset (which is wrong
   for path variables that use filesystem charset)
3. @@signed_int_var in the string context was printed
   as unsigned

it can never be set to NULL, so it should
not use MY_I_S_MAYBE_NULL flag either

old fix only generated a warning for the *first* row
in the output

replace flag SHOW_VALUE_IN_HELP (that's not really an
independendent flag, as it should only be used for
NO_CMD_LINE sysvars) with a special getopt.id type.

their only purpose was to distinguish between
SHOW and SELECT and there are cleaner ways of doing  it.

* ignore the OPTIMIZER_SWITCH_ENGINE_CONDITION_PUSHDOWN bit
* issue a deprecation warning on 'engine_condition_pushdown=on'
* remove unused remains of the old pre-5.5 engine_condition_pushdown variable

MDEV-6606 Server crashes in String::append on selecting sql_mode inside anonymous block