EXPLAIN EXTENDED for an UPDATE/DELETE/INSERT/REPLACE statement did not
produce the warning containing the text representation of the query
obtained after the optimization phase. Such warning was produced for
SELECT statements, but not for DML statements.
The patch fixes this defect of EXPLAIN EXTENDED for DML statements.

note that `KILL USER foo` should *not* fail with ER_KILL_DENIED_ERROR
when SHOW PROCESSLIST doesn't show connections of that user.
Because no connections exist or because the caller has no PROCESS -
doesn't matter.

also, fix the error message to make sense
("You are not owner of thread <current connection id>" is ridiculous)

The error string from ER_KILL_QUERY_DENIED_ERROR took a different
type to ER_KILL_DENIED_ERROR for the thread id. This shows
up in differences on 32 big endian arches like powerpc (Deb notation).

Normalize the passing of the THD->id to its real type of my_thread_id,
and cast to (long long) on output. As such normalize the
ER_KILL_QUERY_DENIED_ERROR to that convention too.

Note for upwards merge, convert the type to %lld on new translations
of ER_KILL_QUERY_DENIED_ERROR.

Use SELECT_LEX to save lists for ORDER BY and GROUP BY before parsing
WINDOW clauses / specifications. This is needed for proper parsing
of a nested WINDOW clause when a WINDOW clause is used in a subquery
contained in another WINDOW clause.

Fix assignment of empty SQL_I_List to another one (in case of empty list
next shoud point on first).