INT 7E - SBOS v3.82 - SET INTERRUPT FOR ???                                     
	AX = 00FFh
	BL = new interrupt vector to hook
Return: BX = 03CDh if supported
Desc:	unhooks the current interrupt handler for ???, and reconnects it to the
	  specified new interrupt number
SeeAlso: AX=00F7h,AX=00F9h,AX=00FEh