INT 21 - Phar Lap 386/DOS-Extender - SET PROTECTED-MODE INTERRUPT VECTOR

	AX = 2504h
	CL = interrupt number
	DS:EDX = CS:EIP of protected-mode interrupt handler
Return: CF clear
Note:	this function is also supported by FlashTek X-32VM
SeeAlso: AX=2502h,AX=2505h,INT 31/AX=0205h