Fix compilation warnings triggered by Python's pyerrors.h

[Eli Zaretskii]

> From: Tom Tromey <tromey@redhat.com>
> Cc: gdb-patches@sourceware.org
> Date: Thu, 14 Mar 2013 11:45:57 -0600
> 
> >>>>> "Eli" == Eli Zaretskii <eliz@gnu.org> writes:
> 
> Eli> Suggested work-around: Define HAVE_SNPRINTF in defs.h:
> 
> Why defs.h and not python-internal.h?

Because I didn't know that all includes of pyerrors.h go through
python-internal.h ;-)

> I think that, if it works, it is better to try to contain the weirdness
> to the Python code.

I agree.  I will make sure it works and commit a modified patch.

Thanks.