INT 15,89 - Switch Processor to Protected Mode

	AH = 89h
	BH = IRQ8 interrupt vector offset
	BL = IRQ0 interrupt vector offset
	CX = offset into protected mode CS to jump
	ES:SI = pointer to Global Descriptor Table (GDT)

	on return:
	CF = 0 if successful
	   = 1 if error

	- switches 286 and 386 machines into protected mode to take
	  advantage of advanced feature and extended memory
	- Global descriptor table must be setup before interrupt
	- normal BIOS functions are not available after the switch