xend: ioport & irq persistence thru reboot

xend: ioport & irq persistence thru reboot

When a domU is configured for a serial port as documented at:
   http://wiki.xensource.com/xenwiki/InstallationNotes

the VM does see the serial port, however when dom0 is rebooted and
the VM started it no longer has access to the serial port.

xm list -l <vm> no longer shows the ioports or irq attributes

Attached patch adds implementation of getDeviceConfiguration(),
returns details dict and implements waitForDevice() to irqif.py and
iopif.py.

Also added preprocess_irq() to create.py.

Signed-off-by: Pat Campbell <plc@novell.com>