[RFA] sh-tdep.c: Follow up patch to implement two different ABIs

[Andrew Cagney]

> I think this patch has too much stuff in it. Can you change it to fix
> the gcc abi (the fpu stuff), and then add the rest for the renesas
> variant?
> 
> 
> 
>  > 
>  > - Add the commands `set calling_convention <foo>' and
>  >   `show calling_convention' with <foo> being one of "gcc" and "renesas".
>  >   Default to "gcc".

FYI, given it's sh specific, it should be:

set/show sh calling-convention <tab>

I suspect there should also be an "auto" option.

Andrew