mail-bury should use one-window-p, not window-dedicated-p

[Drew Adams]

This line in the definition of `mail-bury' should be changed:

 (window-dedicated-p (frame-selected-window))

to this:

(and pop-up-frames (one-window-p))

I use pop-up-frames = t, so that, by default, each buffer gets its own
frame.  That is not the same thing as requiring each window to be
dedicated: I often reuse the same frame for a different buffer, and I
sometimes use `C-x 2' or `C-x 3' to use multiple buffers in the same
frame.  pop-up-frames = t does not prevent using different or multiple
buffers per frame - it does not impose dedicated windows; it simply
says that, by default, you want a new frame, instead of a new window,
created to display a buffer.

When someone uses a one-frame-per-buffer-by-default approach, just as
when someone uses a dedicated-window-per-buffer approach, it is common
to want the frame to be deleted when the buffer is no longer used.

The existing code caters to the latter use case, but it does not DTRT
for the former.  It should delete the frame in both cases.  That is,
it should delete the frame whenever pop-up-frames=t and the window is
alone in the frame.  That covers both use cases, and it doesn't
interfere with the use case of most users: pop-up-frames=nil (whether
one-window-p or not).

Note that `mail-bury' is used not just by people who use gnus, or
even just by people who use Emacs for mail.  It is also used whenever
an Emacs user submits a bug report. So, it is not enough that it
cater to a gnus context; it should fit all expected Emacs use cases.

In GNU Emacs 22.1.50.1 (i386-mingw-nt5.1.2600)
 of 2007-05-22 on LENNART-69DE564
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Ic:/g/include'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  eldoc-mode: t
  display-time-mode: t
  recentf-mode: t
  icomplete-mode: t
  tool-bar-pop-up-mode: t
  icicle-mode: t
  minibuffer-indicate-depth-mode: t
  pretty-control-l-mode: t
  delete-selection-mode: t
  show-paren-mode: t
  encoded-kbd-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  size-indication-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<mouse-movement> <drag-mouse-1> o n e - w i n d o w 
C-h f <return> <down-mouse-1> <mouse-1> <left> C-h 
f <return> <down-mouse-1> <mouse-1> C-h f <return> 
<help-echo> <down-mouse-1> <mouse-movement> <mouse-movement> 
<drag-mouse-1> <backspace> C-M-x <help-echo> <help-echo> 
<help-echo> <menu-bar> <help-menu> <report-emacs-bug> 
m a i l - b u f <backspace> r y SPC s h o u l d SPC 
u s e SPC o n e - w i n d o w - p SPC <backspace> , 
SPC n o t SPC w i n d o w - d e d i c a t e d - p <switch-frame> 
<help-echo> <switch-frame> <return> <switch-frame> 
<help-echo> <down-mouse-1> <mouse-movement> <mouse-1> 
j j j j j j j j j j j j j j j j C-c C-c y e s <return> 
<switch-frame> <down-mouse-1> <mouse-movement> <mouse-1> 
C-M-x <switch-frame> <down-mouse-1> <mouse-movement> 
<mouse-1> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <menu-bar> <help-menu> <report-emacs-bug> 
f f f f f f f f f f f <return> <switch-frame> <down-mouse-1> 
<mouse-movement> <mouse-1> k k k k k k k k k k k k 
C-c C-c y e s <return> <switch-frame> <switch-frame> 
<switch-frame> <switch-frame> <down-mouse-1> <mouse-movement> 
<mouse-1> C-M-x <switch-frame> <switch-frame> C-x 5 
2 <switch-frame> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <menu-bar> <help-menu> <report-emacs-bug> 
f f f f f f f f f <return> <switch-frame> <down-mouse-1> 
<mouse-movement> <mouse-1> f f f f f f f f f f f f 
f f C-c C-c y e s <return> <switch-frame> <switch-frame> 
<switch-frame> <switch-frame> <down-mouse-1> <mouse-movement> 
<mouse-1> C-M-x <switch-frame> <down-mouse-1> <mouse-movement> 
<mouse-1> C-x 5 2 <switch-frame> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> 
<report-emacs-bug> M-p M-p M-p <return> <switch-frame> 
<down-mouse-1> <mouse-1> j j j j j j j j j j j j j 
j j j j C-c C-c y e s <return> <switch-frame> <switch-frame> 
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu> 
<report-emacs-bug>

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