bug#7533: 24.0.50; `dired-mark-pop-up': delete frame afterwards if `pop-up-frames'

[Drew Adams]

> `pop-up-frames' expresses a general preference so I asked 
> Chong to make that change.  `special-display-regexps'
> expresses a special preference.  But if nobody objects we
> can bind things like `special-display-regexps'
> and `special-display-buffer-names' to nil here too.

That's better than nothing, IMO.  It recognizes that this buffer display,
whether in a frame or window, is only temporary, for the duration of the
confirmation interaction: there is no reason to show the buffer after the
command is done.

However, the right fix is to (a) respect a user's preference to show such
buffers in a special frame and then (b) delete the frame.

It is especially not very kosher to override `special-display-buffer-names',
because that option can let users specify not only a buffer name but a specific
function to display it.

IOW, the most important thing in this context is to remove the buffer display
when done.  But it is also important to do what the user wants.

So showing such a buffer in a window instead of a frame should be seen as only a
temporary workaround, since it violates a user preference of using a frame.  It
is a temporary expedient, to obviate the annoyance of not properly handling a
frame in this context.