Fixed the handling of IPL_NONE.
Debugged support for interrupt chaining.
Fill out the intrnames array with the name of the interrupt handler
currently at the head of the chain.
Guarded several sanity checks with #ifdef DIAGNOSTIC.
irq_claim().
Clear the active flag in the irq handler when it is removed from the irq
chain in irq_release().
Checks for podule IRQ's in irq_claim() are now guarded with
#if NPODULEBUS > 0
fiq_release() now retrieves the FIQ more registers and places them
back in the fiq handler structure.
Remove the irq_setmasks() routine. This was coded in assembly months ago
and this C version is now out of date.
Added code for delivering IRQ_SOFTCLOCK.