[patch] update comments on *_ultimate_origin

[Jeff Law]

On 09/18/14 10:42, Aldy Hernandez wrote:
> output_inline_function was removed in tree-ssa times, no sense
> referencing it a decade later.
>
> I still see DECL_ABSTRACT_ORIGIN pointing to itself in some instances,
> though I haven't tracked down where, so I assume we still need the
> functionality, just not the comment :).
>
> OK for mainline?
OK.
jeff