bug#12911: 24.3.50; let users decide where (& perhaps whether) `emacs_backtrace.txt' files are written

[Eli Zaretskii]

> From: Andy Moreton <andrewjmoreton@gmail.com>
> Date: Tue, 20 Nov 2012 13:16:18 +0000
> 
> Given that the backtrace does not include symbols, it seems fairly
> useless to me. I'd vote for getting rid of it on all platforms.

I'd be the last to defend the feature, but out of fairness: symbolic
information (i.e. file names and source line numbers) are one command
away.  See the manual for details.