New model for PowerPC CPU hardware interrupt events:

New model for PowerPC CPU hardware interrupt events:
move all PowerPC specific code into target-ppc/helper.c to avoid polluting
the common code in cpu-exec.c. This makes implementation of new features
(ie embedded PowerPC timers, critical interrupts, ...) easier.
This also avoid hardcoding the IRQ callback in the OpenPIC controller,
making it more easily reusable and allowing cascading.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2542 c046a42c-6fe2-441c-8c8c-71466251a162