Experimental CPU hotplug patch for x86_64
  -----------------------------------------
This supports logical CPU online and offline.
- Test with maxcpus=1, and then kick other cpu's off to test if init code
  is all cleaned up. CONFIG_SCHED_SMT works as well.
- idle threads are forked on demand from keventd threads for clean startup

TBD:
1. Not tested on a real NUMA machine (tested with numa=fake=2)
2. Handle ACPI pieces for physical hotplug support.
Signed-off-by: NAshok Raj <ashok.raj@intel.com>
Acked-by: NAndi Kleen <ak@muc.de>
Acked-by: NZwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Shaohua.li<shaohua.li@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>