Bug#24791: Union with AVG-groups generates wrong results
Bug#24791: Union with AVG-groups generates wrong results

Patch appled after doing a pull from the team tree. Additional tests had to be
fixed


mysql-test/r/union.result:
  Bug 24791
  
  The tests for temporary tables have been fixed. Since the call to 
  display_length(Item) was removed from the constructor for Item_type_holder, items 
  in temporary tables keep the original values of the items, rather than the magic
  numbers supplied by display_length.

ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,slanterns/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,flynn1973/mariadb-aix,ollie314/server,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,davidl-zend/zenddbi,ollie314/server,ollie314/server,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2