[$] Emulated iopl()

Operating systems and computing hardware both carry a lot of their historywith them. The x86 I/O-port mechanism is one piece of that history; it israrely used by hardware designed in the last 20 years, but it muststill be supported. That doesn't mean that this support can't be cleanedup and improved, though, especially when the old implementation turns outto have some unpleasant properties. An example can be seen in theiopl() patch set from Thomas Gleixner.