Improve window/buffer handling code

Improve window/buffer handling code

The purpose of these changes is to improve the code handling the
display of buffers in windows, switching to previous and next
buffers in windows and restoring a previous state after quitting
or killing buffers.  In particular it does:

- Add a new window parameter 'quit-restore-prev' so a window can
keep its initial 'quit-restore' parameter and undoing a sequence
of quit window operations becomes more reliable (Bug#59862).

- Optionally have 'kill-buffer' call 'quit-restore-window' for
all windows showing the argument buffer (Bug#59862).

- Add a new hook so it's possible to avoid that a window gets
deleted implicitly by functions like 'kill-buffer' (Bug#71386).

- Add a new option to make 'quit-restore-window' delete windows
more aggressively (Bug#59862).

- Immediately remove killed buffers from all windows' previous
and next buffers.  For windows that are already dead, use a weak
hash table to be used by 'kill-buffer'.  This avoids any special
handling of such windows by the garbage collector.

- Immediately remove 'quit-restore' and 'quit-restore-prev'
window parameters that reference killed buffers.  These
parameters have no more use once their buffers got killed.

- Make sure that internal windows do not have any previous and
next buffers.  This fixes a silly memory leak.

- Make sure that after set_window_buffer and some wset_buffer
calls the buffer now shown in the window does not appear in the
lists of that window's previous and next buffers.  The old
behavior could make functions investigating these lists
erroneously believe that there still existed some other buffer
to switch to.

* src/alloc.c (mark_discard_killed_buffers): Remove function.
(mark_window): No more filter previous and next buffer lists.
* src/window.h (struct window): Move up prev_buffers and
next-buffers in structure; they are now treated by the collector
as usual.
* src/window.c (window_discard_buffer_from_alist)
(window_discard_buffer_from_list)
(window_discard_buffer_from_window)
(window_discard_buffer_from_dead_windows)
(Fwindow_discard_buffer): New functions.
(set_window_buffer): Discard BUFFER from WINDOW's previous and
next buffers.
(make_parent_window): Make sure internal windows have no previous
and next buffers.
(make_window): Don't initialize window's previous and next
buffers, they are handled by allocate_window now.
(Fdelete_window_internal): Add WINDOW to window_dead_windows_table.
(Fset_window_configuration): Remove resurrected window from
window_dead_windows_table.  Make sure buffers set by wset_buffer
calls are not recorded in window's previous and next buffers.
(delete_all_child_windows): Add deleted windows to
window_dead_windows_table.
(window_dead_windows_table): New weak hash table to record dead
windows that are stored in saved window configurations.
* src/buffer.c (Fkill_buffer): Call new function
'window_discard_buffer_from_dead_windows'.
* lisp/window.el (window-deletable-functions): New hook.
(window-deletable-p): Update doc-string.  Run
'window-deletable-functions' (Bug#71386).
(unrecord-window-buffer): New argument ALL.  Move body to
'window-discard-buffer-from-window' so that if ALL is non-nil,
WINDOW's 'quit-restore' and 'quit-restore-prev' parameters get
removed too.
(switch-to-prev-buffer): Don't care about killed buffers here;
'replace-buffer-in-windows' should have done that already.  Use
'unrecord-window-buffer'.
(switch-to-next-buffer): Don't care about killed buffers here;
'replace-buffer-in-windows' should do that now.
(kill-buffer-quit-windows): New option.
(delete-windows-on): Update doc-string.  Handle new option
'kill-buffer-quit-windows'.  Update 'unrecord-window-buffer'
calls.
(replace-buffer-in-windows): Update doc-string.  Handle new
option 'kill-buffer-quit-windows' (Bug#59862).  Update call to
'unrecord-window-buffer'.
(quit-restore-window-no-switch): New option.
(quit-restore-window): Update doc-string.  Handle additional
values of BURY-OR-KILL so to not kill a buffer about to be
killed by the caller.  Handle 'quit-restore-prev' parameter
(Bug#59862).  Handle new option 'quit-restore-window-no-switch'
(Bug#59862).
(quit-windows-on): Update doc-string.  Call 'quit-window-hook'
and call 'quit-restore-window' directly so that the buffer does
not get buried or killed by the latter.  Update
'unrecord-window-buffer' call.
(display-buffer-record-window): Update doc-string.  Handle new
`quit-restore-prev' parameter (Bug#59862).
(switch-to-buffer): Call 'display-buffer-record-window' so a
latter 'quit-restore-window' can use its parameters.
* doc/lispref/windows.texi (Deleting Windows): Describe implicit
deletion of windows and new hook 'window-deletable-functions'.
(Buffers and Windows): Update description of
'replace-buffer-in-windows'.  Describe new option
'kill-buffer-quit-windows'.
(Quitting Windows): Describe 'quit-restore-prev' parameter and
new option 'quit-restore-window-no-switch'.  Update description
of 'quit-restore-window'.
(Window Parameters): Mention 'quit-restore-prev' parameter.
* etc/NEWS: Add entries for 'window-deletable-functions',
'kill-buffer-quit-windows', 'quit-restore-window-no-switch'.
mention new parameter 'quit-restore-prev' and new argument
values for 'quit-restore-window'.

(cherry picked from commit 27381d71c65bd0ba93ed61f57011dbc66bd5bfab)