Fix handling of debugger window. (Bug#8789)

* window.el (display-buffer-in-previous-window): New buffer
display action function.

* emacs-lisp/debug.el (debugger-bury-or-kill): New option.
(debugger-previous-window): New variable.
(debug): Rewrite using display-buffer-in-previous-window,
quit-restore-window and debugger-bury-or-kill.  (Bug#8789)