We now can boot without MPS and PIRQ!
ACPI finds IO APICs, Local apics (CPUS), interrupt source overrides,
the works. (Paul Diefenbaugh) Mucho thanks to Dominik Brodowski and
the whole acpi-devel gang.

(Note, I think this conflicts slightly with Pavel's code in i386/kernel/acpi.c
but I'd like to get this applied, and then I'm working with Pavel to hopefully
get the ACPI and swsusp stuff working properly.)