mysql-test/r/subselect.result:
  result changing
  fixed last test
  test of transformation of left expression of subquery
mysql-test/t/subselect.test:
  fixed last test
  test of transformation of left expression of subquery
sql/item_subselect.cc:
  fixfields made for left part of IN/ALL/ANY subquery before calling cols() to detect type of transformation (scalar or row)
  similar action of both transformation moved to separate function
sql/item_subselect.h:
  optimised field initialization and new method