gistfile1.el

(defun bertl-switch-to-buffer (name)
  (interactive "BSwitch to buffer")
  (let ((buffer (get-buffer name)))
    (if buffer
	(switch-to-buffer buffer)
      (progn
	(switch-to-buffer name)
	(setq buffer-offer-save t)
	(auto-save-mode t)))))

(defun bertl-kill-buffer-function ()
  (let ((buffer (current-buffer)))
    (when (and buffer-offer-save
	       (buffer-modified-p buffer)
	       (y-or-n-p (concat "Save buffer " (buffer-name buffer) "? ")))
      (save-buffer)))
  t)

(setq kill-buffer-query-functions (append '(bertl-kill-buffer-function) kill-buffer-query-functions))