Identifying some functionality all architectures have and trying to
make a common interface.

Squash review:
intrcompat: add "interrupt_t" typedef for all architectures

For code which doesn't care about the underlying structure and simply
needs to have a common name.

intrng: add standard interrupt controller interface

Interrupt numbering belongs to the interrupt controller, not the core
event code. As such, this layer should be providing a function to
resolve the interrupt number to the source/event.

powerpc: add ability to access intr_event by interrupt number

Most other systems have this via INTRNG or other means. Now add the
functionality to PowerPC.

intr/x86: implement standard interrupt interface

Different name for the main function, but then a simple macro on top.