bug#34186: 26.1; locking up

[Eli Zaretskii]

> From: Michael Menefee <mpmenefee@gmail.com>
> Date: Thu, 24 Jan 2019 10:32:34 -0600
> Cc: 34186@debbugs.gnu.org
> 
> I have found the minimum necessary to consistently reproduce.  copy/paste 
> this into something.c to see if you
> get same results:
> 
> void *AVL_first(AVL_t *);
> void *AVL_last(AVL_t *);
> #define (<--- locks up with pressing open parenthesis

Thanks, now I can reproduce this.  Alan, please take a look.