raw_switch:

	Provides the code to switch between real and protected mode.
	Switches between the environments "completely":
	e.g. when switching to protected mode,
	all the normal protected-mode state for that environment is set up.

raw_pmode:

	i16_raw_enter_pmode()
		Enters protoected mode from real mode.
		Does not initialize IDT or TSS or anything else;
		just gets the system into protected mode
		with a simple temporary GDT.
		Returns with interrupts turned off
		(and they'd better stay off until there's a valid pmode IDT!)

	i16_raw_leave_pmode()
		Assumes paging is turned off.
		Returns with interrupts turned off;
		they can probably be turned back on at any time.

	Depends on:
		i16_die()
		A20 enable/disable code (e.g. raw_a20).
		gdt.h: KERNEL_16_CS, KERNEL_16_DS



vm_param.h:

	Must export kvtolin(), lintokv()