[PATCH, ARM] Don't use __thumb2__ to select _REENT_SMALL

[Paul Brook]

> >> That said, I agree with Richard's point.  If the thumb2 flag is not a
> >> proper check for a platform that requires a small reent struct, then it
> >> shouldn't be used as such.
> >
> > Well, the whole idea that this is something that can be figured out from
> > the target is wrong. It should really be a user visible configure option.
>
> Do you mean the existing --enable-newlib-reent-small configure option or
> something different?

Yes, exactly that.  In that case I suggest removing the __thumb2__ check 
altogether.  It would be nice if reent-small didn't break the library ABI, but 
that's a different issue.

Paul