RE: warning about undo info being discarded when in *Backtrace*

["Drew Adams" <drew.adams@oracle.com>]

> How about turning off undo information in *Backtrace*?
> As far as I know, there is no use for any.

I almost mentioned that too. I did not, thinking that someone might want to
edit a sexp in the buffer to use as a return value, and then undo the edit
to see better what was there before, etc. Or s?he might want to paste a
value into the buffer as return value, and use undo during editing of the
value in place.

Ohter than a use such as that, I can't think of a good reason for having
undo in *Backtrace*.

I didn't try the patch (but it would seem to turn off undo OK).