Now that all arches (for the most part) have moved over, move sim-stop.o,
sim-reason.o, and sim-reg.o to the common object list and out of all the
arch ports.
Now that all the targets are utilizing CPU_PC_{FETCH,STORE}, and the
cpu state is multicore, and the STATE_CPU defines match, we can move
it all to the common code.
We want people to stop using the run.c frontend, but it's hard to notice
when it's still set as the default. Lets flip things so nrun.c is the
default, and users of run.c will get an error by default. We turn that
error into a warning for existing sims so we don't break them -- this is
mostly meant for people starting new ports.
