bug#17598: Emacs pretest 24.3.91 - AIX - SIGSEV when customize

[Paul Eggert]

Eli Zaretskii wrote:

> The changes to lisp.h intended to enhance debugging on AIX broke
> debugging when GCC 3.x is used to compile the code: I get "No symbol
> "VALMASK" in current context." when xbacktrace is invoked.

Sorry about that.  It appears you ran into GCC bug 23336, an old bug I 
wasn't familiar with.  By the time this bug was fixed in 2006, the GCC 
folks had stopped maintaining GCC 3.x.  See:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=23336

> I hope there's a way to
> define the relevant macros only for AIX, so that other platforms
> aren't affected, certainly not during the pretest.

I gave that a shot in emacs-24 bzr 117185.