renamed tables to prevent droping real tables


mysql-test/r/group_by.result:
  test of error message
mysql-test/r/subselect.result:
  renamed tables to prevent droping real tables
mysql-test/t/group_by.test:
  test of error message
mysql-test/t/subselect.test:
  renamed tables to prevent droping real tables
sql/sql_base.cc:
  moved thd->allow_sum_func assignment to upper level
sql/sql_select.cc:
  fixed removed by previos patch thd->allow_sum_func "side effect" of setup_conds