||Deletes a record number from the marking list of a table
||DELMARK(db : INTEGER; recno : INTEGER) : INTEGER
||db : table handle from OPENDB
recno : physical number of record
||Number of record which is deleted from the marking list (recno).
The record with the physical record number recno is deleted from the marking list of the table.
If the record is not in the marking list NO error occurs.