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

[Drew Adams]

> > I sent an emacs-backtrace.txt file recently
> 
> Where?  I must have missed that, or maybe forgot.

The first mail that started this discussion:
http://debbugs.gnu.org/cgi/bugreport.cgi?bug=12908

This is the exchange we had about it:

EZ>>>> Users should include it with their bug reports.
DA>>> 
DA>>> Does my having included it in this bug report help in some
DA>>> way?  I'm guessing no, but would love to be shown wrong.
EZ>>
EZ>> Your guess is wrong, that file includes enough information
EZ>> to understand where the crash happened, and in some cases
EZ>> also why.
DA>
DA> That's good news.  Let's hope it helps fix some of the
DA> crashing problems.