INT 15 - MultiDOS Plus - UNMAP IRQ
AH = 18h
AL = IRQ to unmap (01h-0Fh)
Return: AX = status
0000h successful
0001h invalid IRQ
Note:   results are unpredictable if the IRQ has not been mapped
SeeAlso: AH=19h"MultiDOS"

See also: 1517

1518 - MultiDOS Plus - UNMAP IRQ