OK, the grand finale ... NUMA-Q is now moved into subarch, so we can
kill off the last vestiges - CONFIG_CLUSTERED_APIC, clustered_apic_mode,
and smpboot.h (which only contains machine specific stuff now anyway).
the esr_disable switch was the last bit, that goes to subarch too.

If you end up with an empty smpboot.h due to patch / bitkeeper interactions,
please remove it after this ...