x86 port of generic hardirq handling.

akpm: (in response to build errors)

- remove APIC_MISMATCH_DEBUG altogether.  Just make it synonymous with
  CONFIG_X86_IO_APIC

- Move the definition of irq_mis_count over to io_apic.c
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>