mysql-test/r/subselect.result:
  test of new optimisation
mysql-test/t/subselect.test:
  test of new optimisation
sql/item_subselect.cc:
  special subselect to finding max/min of returned values
  optimisation of independent ALL/ANY with aggregate function
sql/item_subselect.h:
  special subselect to finding max/min of returned values
sql/sql_class.cc:
  class for collaction result for max/min subquery
sql/sql_class.h:
  class for collaction result for max/min subquery