Method is_fatal_error

This method is used to analyse the error to see whether the error is ignorable or not, certain handlers can have more error that are ignorable than others. E.g. the partition handler can get inserts into a range where there is no partition and this is an ignorable error. HA_ERR_FOUND_DUP_UNIQUE is a special case in MyISAM that means the same thing as HA_ERR_FOUND_DUP_KEY bu