bug#21006: 25.0.50; xref-quit doesn't restore changes in window scrolling position

[Dmitry Gutov]

1. Open lisp/progmodes/elisp-mode.el.

2. M-x xref-find-regexp, type 'defun elisp-[a-z]' (without quotes) when
prompted, press RET.

3. In the xref buffer, press `n' a couple of times, see the window
displaying elisp-mode.el scroll to show the definitions.

4. Press `q', see the previous window configuration restored, but the
scrolling position of the elisp-mode.el window remains changed.

I wonder if we can do anything about that.

While there's nothing surprising in this behavior given the
implementation, the user did lose their position in the buffer, train of
thought, etc.