[RFC/AIX] xm-aix4.h - Can we remove NULL re-define?

[Andrew Cagney]

> config/xm-aix4.h contains the following definition:
> 
> | /* Brain death inherited from PC's pervades.  */
> | #undef NULL
> | #define NULL 0

I'd assume that the PC perversity was along the lines of either:
	-- NULL not defined
	-- #define NULL ((void *)0)
where PC is AIX running on an i386 (yea, right :-).

> Is this still needed? Where does this come from?
> 
> It looks pretty scary that a compiler would actually defined NULL
> as being non-zero. I have always heard that NULL is not garantied
> to be zero, but I've seen so much code kind of confusing NULL and
> zero that I thought nobody in their right mind would actually do
> otherwise...
> 
> If still necessary, can this be replaced by something like this in
> defs.h?
> 
>         #if (NULL != 0)
>         #undef NULL
>         #define NULL 0
>         #endif

So just delete it.

Andrew