Problem: caching 00000000-00000099 dates as integer values we're 
improperly shifting them up twice in the get_datetime_value().
  
Fix: don't shift cached DATETIME values up for the second time.


mysql-test/r/type_date.result:
  Fix for bug #32021: Using Date 000-00-01 in WHERE causes wrong result
    - test result.
mysql-test/t/type_date.test:
  Fix for bug #32021: Using Date 000-00-01 in WHERE causes wrong result
    - test case.
sql/item.h:
  Fix for bug #32021: Using Date 000-00-01 in WHERE causes wrong result
    - Item_cache::field_type() method added.
    - new Item_cache(enum_field_types) and Item_cache_int(enum_field_types) 
      constructors added.
sql/item_cmpfunc.cc:
  Fix for bug #32021: Using Date 000-00-01 in WHERE causes wrong result
    - don't shift cached DATETIME values for the second time in the
      get_datetime_value():
        creating new Item_cache_int set DATETIME filed type,
        check the type before shifting.