used

In a simple queries a result of the GROUP_CONCAT() function was always of 
varchar type.
But if length of GROUP_CONCAT() result is greater than 512 chars and temporary
table is used during select then the result is converted to blob, due to
policy to not to store fields longer than 512 chars in tmp table as varchar
fields.

In order to provide consistent behaviour, result of GROUP_CONCAT() now
will always be converted to blob if it is longer than 512 chars.
Item_func_group_concat::field_type() is modified accordingly.


sql/item_sum.h:
  Fixed bug#14169: type of group_concat() result changed to blob if tmp_table was 
  used
  The Item_func_group_concat::field_type() now returns FIELD_TYPE_BLOB if the result is longer than 512 chars.
tests/mysql_client_test.c:
  Added test case for bug#14169: type of group_concat() result changed to blob if tmp_table was used