mysql-test/r/type_datetime.result:
  result for datetime fix
mysql-test/t/type_datetime.test:
  test for datetime fix
sql/sql_select.cc:
  Fix for a bug caused implicitely by MySQL having to comply with 
  ODBC standard on datetime comparisons.
  
  This failed to update used_tables() for OR condition, which is why
  query returned all rows on query as in .test above, while
  none of types contains NULL nor 0 datetime (last one from ODBC)