gcc4 complains about multiple definitions of irq_affinity--I think the one in 
arch/ia64/kernel/irq.c is the redundant one since the array is also defined 
in kernel/irq/manage.c.

Building with gcc4 generates a bunch of warnings too, saying that qualifiers 
on function return types are being ignored (in particular the ones from 
__ia64_get_io_port_base and the ones having to do with mmu_context_t being 
volatile).  Should we use attribute(const) for get_io_port_base?  What about 
for the mmu_context_t functions?

Signed-off-by: Jesse Barnes <jbarnes@sgi.com>

Jesse