Support the I/O APIC alongside the 8259 PIC

See merge request !117

since this would require pcid to know the _PRT (PCI routing table) to
use and map the interrupt pins to the correct IRQs. xhcid is unaffected
by this though, since it uses MSI-X.

All ACPI handling will be done in userspace before the infrastructure
necessary would make sense (I don't think adding serde to the kernel
would be optimal, and how else would all of the ACPI namespace be
parsed?).

and fix a typo that prevented multiple tables from being listed
correctly.

which tells the firmware that the I/O APIC is used rather than the 8259
PIC.

which tells the firmware that the I/O APIC is used rather than the 8259
PIC.

Replace Arc<Box<dyn Scheme>> with Arc<dyn Scheme>.

See merge request !116

Extend the IRQ scheme to allow allocation of all available interrupt vectors.

See merge request !115

I haven't been able to receive xhc interrupt anyway.

Fix warnings

See merge request !114