Since the irq handling rework in 2.5 lots of code in the individual
<asm/hardirq.h> files is the same.  This patch moves that common code
to <linux/hardirq.h>.  The following differences existed:

 - alpha, m68k, m68knommu and v850 were missing the ~PREEMPT_ACTIVE
   masking in the CONFIG_PREEMPT case of in_atomic().  These
   architectures don't support CONFIG_PREEMPT else this would have been
   an easily-spottbale bug
 - S390 didn't provide synchronize_irq as it doesn't fit into their
   I/O model.  They now get a spurious prototype/macro
 - ppc added a new preemptible() macro that is provided for all
   architectures now.

Most drivers were using <linux/interrupt.h> as they should, but a few
drivers and lots of architecture code has been updated to use
<linux/hardirq.h> instead of <asm/hardirq.h>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>