row_ins_foreign_check_on_constraint(): When constructing
cascade->historical_row for tables WITH SYSTEM VERSIONING,
use the appropriate mode ROW_COPY_DATA, because the pointers
will be stale after mtr_commit() is invoked.
Make foreign system versioning tables work in CASCADE UPDATE/SET NULL.
In that case basically row update is performed. This patch makes insert
of a historical row performed too.
row_update_versioned_insert(): restores btr_pcur_t, reads row from it, makes
row historical and inserts to table.
row_ins_check_foreign_constraint(): disable constraint check for historical
rows because it has no sense. Also check will fail always, because referenced
table is updated at that point.
row_update_cascade_for_mysql(): insert historical row for system versioning
tables before updating current row.
revert DATA_VERSIONED -> DATA_UNVERSIONED