[patch, fortran] use vec<> in frontend-passes.c

[Tobias Burnus]

Hi Thomas, hi all,

first, thanks Trevor for the first round of review!

Thomas Koenig wrote:
> Trevor Saunders wrote:
> > >    doloop_warn (ns);
> > > -  XDELETEVEC (doloop_list);
> > > +  doloop_list.truncate (0);
> >
> > .release () would be more typical.
>
> Changed (also below).

I still see:
> -  expr_count = 0;
> +  expr_array.truncate (0);

Is there is a reason for not using release() here?

Otherwise, it looks good to me - and cleaner than the home-grown stack.

Tobias