Actions for annulment - Natural or legal persons - Measures of direct and individual concern to them - Regulation introducing a fixed date for the determination of the rate of conversion into national currency of the premium for tobacco from harvests prior to 1993 (EC Treaty, Art. 173, fourth para., and Art. 189; Commission Regulation No 3477/93, Art. 5, Art. 6, first indent, and Art. 7, second para.)