buff-menu: Add command to unmark all buffers

Bind 'U' in buff-menu, bs and electric-buff-menu to commands
to unmark all buffers (Bug#24880).
* lisp/emacs-lisp/tabulated-list.el (tabulated-list-header-overlay-p):
New predicate; return non-nil if tabulated-list has a fake header.
* lisp/buff-menu.el (Buffer-menu-unmark-all-buffers):
New command; remove all flags that use a particular mark from all the lines.
Bind it to 'M-DEL'.
(Buffer-menu-unmark-all):
New command; remove all flags from all the lines.  Bind it to 'U'.
(Buffer-menu-marker-char, Buffer-menu-del-char): New variables.
(Buffer-menu-delete, Buffer-menu-mark): Use them.
(Buffer-menu-mode-map): Update menus.
(Buffer-menu-mode): Update mode doc.
* lisp/bs.el (bs-unmark-all, bs-unmark-previous): New commands.
(bs-mode-map): Bind them to 'U' and '<backspace>' respectively.
(bs-mode): Update mode doc.
* lisp/ebuff-menu.el (electric-buffer-menu-mode-map):
Bind Buffer-menu-unmark-all to 'U' and Buffer-menu-unmark-all-buffers
to 'M-DEL'.
(bs--down, bs-down, bs--up, bs-up, bs-unmark-current, bs-mark-current):
Use point instead of cursor in doc string.
(electric-buffer-list): Update mode doc.
* doc/emacs/buffers.texi (Several Buffers): Mention Buffer-menu-unmark-all
and Buffer-menu-unmark-all-buffers.
; * etc/NEWS: Add an entry per each new feature.

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/emacs/buffers.texi b/doc/emacs/buffers.texi
index 2eb837f1510..c70e583b9ed 100644
--- a/doc/emacs/buffers.texi
+++ b/doc/emacs/buffers.texi
@@ -411,6 +411,18 @@ Remove all flags from the current line, and move down
 @kindex DEL @r{(Buffer Menu)}
 Move to the previous line and remove all flags on that line
 (@code{Buffer-menu-backup-unmark}).
+
+@item M-@key{DEL}
+@findex Buffer-menu-unmark-all-buffers
+@kindex M-DEL @r{(Buffer Menu)}
+Remove a particular flag from all lines
+(@code{Buffer-menu-unmark-all-buffers}).
+
+@item U
+@findex Buffer-menu-unmark-all
+@kindex U @r{(Buffer Menu)}
+Remove all flags from all the lines
+(@code{Buffer-menu-unmark-all}).
 @end table
 
 @noindent