Most of code originally by James Cleverdon.

More stuff reformed in the mpparse sections - this time not apic stuff,
so we create mach_mpparse.h and stick it in there.

Abstracts out:
 - mpc_oem_bus_info() - stores mappings between buses and nodes/quads.
 - mpc_oem_pci_bus()  - stores mappings between global and local pci bus numbers

Changes summit_check() into mps_oem_check() to generalise it.