INT 21 - Phar Lap 386/DOS-Extender - GET REAL-MODE INTERRUPT VECTOR

	AX = 2503h
	CL = interrupt number
Return: CF clear
	EBX = CS:IP of real-mode interrupt handler
Note:	this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2504h,AH=35h,INT 31/AX=0200h