bug#8789: 23.3; debug backtrace buffer changes window on step-through

[Drew Adams]

There seem still to be problems.

emacs -Q

M-x load-file MARTIN-debug.elc

;; That's debug.el, with your patch.
;; If I load the .el instead of the .elc, then the debugger is
;; called even for implement-debugger etc. - a mess.

M-x load-library files.el

M-x debug-on-entry file-remote-p

That puts me immediately into the debugger, with a call to `file-remote-p'.  Why
does debugging file-remote-p cause the debugger to enter even for that M-x
invocation?  There is not even any reading of a file name.

Thereafter, I cannot exit the debugger, no matter what I do.  `c' and `q' seem
to do nothing.  `d' just steps into `file-remote-p'.  Even `C-]' does not exit
the debugger.  I can use C-x k to kill the *Backtrace* buffer, but that leaves
Emacs in a recursive edit, and `C-]' then brings Emacs back into the debugger.
After the `C-x k', *Messages* shows this multiple times, always ending by
entering:

Entering debugger...
Quit
Entering debugger...
Quit
Entering debugger...
Quit
Entering debugger...
Quit
Entering debugger...

This really seems to be a mess.  For me, the debugger is not usable now, even
with emacs -Q.