interrupt block). We use the previously hardcoded address as a
default only, but will otherwise use whatever ACPI tells us.
The address can be found in the MADT table header or in the
LAPIC override table entry.
not work on any real hardware (or fully work on any simulator). Much more
needs to happen before this is actually functional but its nice to see
the FreeBSD copyright message appear in the ia64 simulator.
