Re: [RFC/AIX] xm-aix4.h - Remove USG #define

[Andrew Cagney <cagney@gnu.org>]

>   Date: Sat, 7 Aug 2004 21:46:49 -0700
>    From: Joel Brobecker <brobecker@gnat.com>
> 
>    config/xm-aix4.h has the following definition:
> 
>    | #define USG 1
> 
>    The most obvious way of getting rid of it is to add a piece in configure.in
>    to set this define if on AIX by adding a -D to the cflags, but that
>    would be ugly. I think the best approach would be to see if we couldn't
>    just get rid of its usage entirely. Need to review its usage first...
> 
> The USG define just really has to go.  Given the fact that GDB
> compiles without problems on many SystemV-ish systems without the
> define, my guess is that it can be eliminated.  Just try what happens
> if you delete it on the oldest AIX system you can find.

Right, as a reference, `break main; run' still worked on IRIX 6.5 after 
#define USG was removed from it's config.

However, lets just define `oldest AIX system' to mean `>=4.3 AIX system'.

Andrew