"CSV does not work with NULL value in datetime fields"
  Attempting to insert a row with a NULL value for a DATETIME field
  results in a CSV file which the storage engine cannot read.
  Don't blindly assume that "0" is acceptable for all field types,
  Since CSV does not support NULL, we find out from the field the
  default non-null value.
  Do not permit the creation of a table with a nullable columns.


mysql-test/r/csv.result:
  test for bug 31473
mysql-test/r/log_tables.result:
  change in results due to bugfix 31473
mysql-test/r/system_mysql_db.result:
  change in results due to bugfix 31473
mysql-test/t/csv.test:
  test for bug 31473
mysql-test/t/log_tables.test:
  due to bug31473, all columns in CSV tables must be declared as NOT NULL
scripts/mysql_system_tables.sql:
  due to bug31473, all columns in CSV tables must be declared as NOT NULL
storage/csv/ha_tina.cc:
  bug31473
    Don't blindly assume that "0" is acceptable for all field types,
    Since CSV does not support NULL, we find out from the field the
    default non-null value.
    Do not permit the creation of a table with a nullable columns;