Add the necessary bits to enable kernel breakpoints for Book-E. The entrypoint
for program exception is very trivial, so rather than expand it to be similar to
AIM, add it into the standard trap handler.
This wasn't blocked out as Book-E specific because it is only a minor redundancy
over AIM, which should have already called db_trap_glue() at this point. If
it's going to panic with a fatal trap anywya, it doesn't matter if it goes
through this path again.
15fc4ab7fc