the 32 interrupts limit is gone

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hi,
I just commited the code which removes the limit on the number of active
events in NetBSD/xen. A NetBSD kernel can now use all the 1024 available
events at once (we're now better than linux, as the 2.6.10-XEN0 kernel is
limited to 128 active events :)

Based on idea from YAMAMOTO Takashi, I've duplicated the interrupt handlers
in 2 lists: one per-event, and one per-IPL. If the IPL is low enouth for the
event to be delivered immediatly, we can access the relevant handler(s)
directly. Otherwise, we mark the IPL as pending, and will run all the
handlers of the given IPL at spllower() time. This allows to keep the
bitmask used for the spl stuff small enouth to use single-instruction
operations.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--