hoo boy, interrupt Handling on BGQ

[Jimi Xenidis]

So interrupts need to go to FW before Linux, please let not talk about how silly that is.
Lets talk about something far more silly...
In order to get to the Linux exception handlers, we have to tell FW where the interrupt page is, and then it _copies_ it.

IFAICT, this means that each vectors on the "copied" page must:
1) construct an 64-bit absolute address to a per vector stub
2) leap at the (with bctr or blr)
3) restore CTR or LR and anything else that (1) messed up
4) normal branch to the actual vector

This is what I'll be working on, but I'd love to hear any other ideas.
-jx