away.

Additional fix for bug#22331. Now Item_field prints its value in the case of
the const field.


mysql-test/r/varbinary.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/union.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/subselect.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/func_test.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/having.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/func_regexp.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/func_str.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/func_default.result:
  Corrected test case after fix for bug#22331.
mysql-test/r/explain.result:
  Corrected test case after fix for bug#22331.
sql/sql_union.cc:
  Bug#22331: Wrong WHERE in EXPLAIN EXTENDED when all expressions were optimized
  away.
  Cleanup of the SELECT_LEX::order_list list.
sql/item.h:
  Bug#22331: Wrong WHERE in EXPLAIN EXTENDED when all expressions were optimized
  away.
  Added the print() member function to the Item_field class.
sql/item.cc:
  Bug#22331: Wrong WHERE in EXPLAIN EXTENDED when all expressions were optimized
  away.
  Added the print() member function to the Item_field class.