Add support for target switches in simulator

[Nick Clifton]

Hi Richard,

> > > How does this proposed facility compare to that provided by
> > > sim/common/sim-options*?
> > 
> > It is a similar kind of thing accept that it has two advantages:
> > 
> >   * It works for simulators that do not use sim-common.[ch]  (such as
> >     the ARM simualtor).
> 
> Is there a good reason why the ARM simulator is not using sim-common?

I doubt it.  I suspect that it is just a historical thing.

Cheers
        Nick