When a UNION statement forced conversion of an UTF8
charset value to a binary charset value, the byte
length of the result values was truncated to the
CHAR_LENGTH of the original UTF8 value.


sql/item.cc:
  Fixed bug #29205.
  The calculation of data length was modified in
  the Item_type_holder::join_types method to take into
  account possible conversion of a multibyte charset
  value to a binary charset value, when each
  multibyte character is converted into a sequence
  of bytes (not to a single byte of binary charset).
mysql-test/t/ctype_utf8.test:
  Updated test case for bug #29205.
mysql-test/r/ctype_utf8.result:
  Updated test case for bug #29205.