Better fix for ON DUPLICATE KEY UPDATE


mysql-test/r/group_by.result:
  After merge fixes
mysql-test/r/select.result:
  Reorder test to match 4.1 tests (will make future merges easier)
mysql-test/t/group_by.test:
  Added --disable_ps_protocol to avoid extra warning
mysql-test/t/select.test:
  Reorder test to match 4.1 tests (will make future merges easier)
sql/mysql_priv.h:
  Better fix for ON DUPLICATE KEY UPDATE
sql/sql_base.cc:
  After merge fixes
sql/sql_insert.cc:
  Better fix for ON DUPLICATE KEY UPDATE
  (old solution gave problem with item->cached_table)
sql/sql_prepare.cc:
  Better fix for ON DUPLICATE KEY UPDATE