[RFA] AiX: enable thread support only if libpthdebug is recent enough

[Joel Brobecker <brobecker@gnat.com>]

Hello,

The build is broken for me on AiX 4.3.2.0 because aix-thread.c assumes
a more recent version of lib pthdebug that is actually installed. I have
therefore made the following changes to enable the thread support only
if the pthread debug lib is at least version 3. 

I know the build works with version 3, and it may be that it works for
version 2 as well. But I can't check this, so I played it safe for now.
If it turns out that it works with version 2 as well, then we can very
easily change it.

Since the build is also broken on the 5.3 branch for the same reason, 
I suggest this patch be applied to the 5.3 branch as well.

2002-11-27  J. Brobecker  <brobecker@gnat.com>

        * configure.in: Check that the pthdebug library is recent enough
        before enable thread support on native AiX.
        * configure: Regenerate.

        * config/powerpc/aix432.mh (NATDEPFILES): Remove aix-thread.o
        from the list of object files as it is now appended by configure
        if thread support is enabled.
        (NAT_CLIBS): Removed as -lpthdebug is also appended by configure
        if thread support is enabled.

Ok to commit? Ok for 5.3 as well?
(I did not include the diff for configure, as this is a generated file)

Thanks,
-- 
Joel