proper handling of SUM() in some functions.



BitKeeper/etc/logging_ok:
  auto-union
sql/item_cmpfunc.cc:
  Auto merged
sql/item_cmpfunc.h:
  Auto merged
sql/item_func.cc:
  Auto merged
sql/item_func.h:
  Auto merged
sql/item_strfunc.cc:
  Auto merged
sql/mysql_priv.h:
  Auto merged
sql/sql_db.cc:
  Auto merged
sql/sql_show.cc:
  Auto merged
sql/table.cc:
  Auto merged
mysql-test/r/group_by.result:
  merge with 3.23.56
mysql-test/t/group_by.test:
  merge with 3.23.56
sql/item_strfunc.h:
  merge with 3.23.56
sql/mysqld.cc:
  merge with 3.23.56
sql/sql_parse.cc:
  merge with 3.23.56
sql/sql_yacc.yy:
  merge with 3.23.56