this implementation have limitation: prohibited subselect in ORDER BY dependence of most outer query (will be solved after removing passing first select_lex as fake select for global mysql_select())


mysql-test/r/subselect.result:
  test of subselect in global ORDER BY
mysql-test/t/subselect.test:
  test of subselect in global ORDER BY
sql/sql_lex.cc:
  fixed comments
  processing of subselect in global ORDER BY
sql/sql_lex.h:
  processing of subselect in global ORDER BY
sql/sql_parse.cc:
  processing of subselect in global ORDER BY
sql/sql_yacc.yy:
  processing of subselect in global ORDER BY