libxl/xl: implement support for guest ioport and irq permissions.

libxl/xl: implement support for guest ioport and irq permissions.

This is useful for passing legacy ISA devices (e.g. com ports,
parallel ports) to guests.

Supported syntax is as described in
http://cmrg.fifthhorseman.net/wiki/xen#grantingaccesstoserialhardwaretoadomU

I tested this using Xen's 'q' key handler which prints out the I/O
port and IRQ ranges allowed for each domain. e.g.:

(XEN) Rangesets belonging to domain 31:
(XEN)     I/O Ports  { 2e8-2ef, 2f8-2ff }
(XEN)     Interrupts { 3, 5-6 }

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Tested-by: Dieter Bloms <dieter@bloms.de>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>