PATCH[b-i=b]: Change cpp_hashnode.directive_index to a bit-field

[Robert Lipe]

> > I wonder:  Are there actually still any machines that have signed
> > bitfields, supported as gcc hosts?
> 
> Yes.  This came up in the real.c rewrite as well.  I don't
> recall whose bootstrap compiler it was, but you could look
> for the antecedent to 
> 
> 2002-10-03  Richard Henderson  <rth@redhat.com>
> 
>         * real.h (struct real_value): Use ENUM_BITFIELD.

I think that would be OpenServer.  It uses signed bitfields (as ISO
allows it to do) AFAIR.   I'm not within reach of a tree right now, but
if ENUM_BITFIELD appears in a ChangeLog with my name on it, that would
be the victim^Wreason.

RJL