[RFA] Basic structure to describe register formats

[Andrew Cagney]

Almost approved,  I've been pokeing at random targets that once worked 
and they have now all been broken by multi-arch.

> @@ -0,0 +1,28 @@
> +name:arm
> +resume:r11,sp,pc
> +4:r0
> +4:r1
> +4:r2


My only quarm is with this.  It extends the G packet definition a little 
- lines with a leading letter get ignored just like comments and blanks. 
  Correct?

Any way I think EXPEDITE to better word for describing what is to be 
done with those registers.  SID uses that word to describe this exact 
same list.

Andrew