INT 15,C4 - Programmable Option Select (PS/2)

	AH = C4
	AL = 0	get Programmable Option Select adapter register address
	   = 1	enable slot for setup
	   = 2	adapter enable


	on return:
	CF = 0 if successful
	   = 1 if error
	AH = when CF set, 80h for PC & PCjr, 86h for XT, AT & 30
	BL = slot number (function AL=1)
	DL = POS adapter register address (function AL=0)


	- allows access to PS/2 Programmable Option Select registers
	- available on 80286 and 80386 PS/2's