mysql-test/r/subselect.result:
  depended subselect test
mysql-test/t/subselect.test:
  depended subselect test
sql/item.cc:
  resolving field names in depended queries
sql/item_subselect.cc:
  move optimization just before execution, because we can't optimize inner depended subselect if have not optimized outer subselect
sql/item_subselect.h:
  move optimization just before execution
sql/sql_lex.h:
  some inline methods to hide internal SELECT_LEX structures
sql/sql_select.cc:
  fixed error