special-display-popup-frame should have BUFFER current when it calls make-frame

[Drew Adams]

This problem existed in Emacs 20. I'm not positive that this change needs to
be made to Emacs 21, but comparing the code to the Emacs 20 code, I believe
the change still needs to be made.

The problem is that, when a new frame is created because no window exists
yet, the call to make-frame does not happen with BUFFER current. This can
have undesirable consequences for, for instance, after-make-frame-functions
that might depend on which buffer is current.

The code should be changed from this:

(make-frame (append args special-display-frame-alist))

to this:

(save-excursion (set-buffer buffer)
                (make-frame (append args special-display-frame-alist)))