Customize tabulated-list sort indicators

This allows the user to customize the sorting indicators displayed
near the current column.

* lisp/emacs-lisp/tabulated-list.el (tabulated-list): New group.
(tabulated-list-gui-sort-indicator-asc)
(tabulated-list-gui-sort-indicator-desc)
(tabulated-list-tty-sort-indicator-asc)
(tabulated-list-tty-sort-indicator-desc): New defcustomd.
(tabulated-list-glyphless-char-display): Remove.
(tabulated-list-make-glyphless-char-display-table): New function.

* doc/lispref/modes.texi (Tabulated List Mode): Add documentation
for new options.

* etc/NEWS: Mention the new options.

1 files changed, 12 insertions, 1 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 31772abe6c7..000d211c1ab 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -923,7 +923,7 @@ been instrumented by Edebug.
 the XTerm window title.  This feature is experimental and is disabled
 by default.
 
-** grep
+** Grep
 
 +++
 *** rgrep, lgrep and zrgrep now hide part of the command line
@@ -1194,6 +1194,17 @@ the 128...255 range, as expected.
 This allows to create and parent immediately a minibuffer-only child
 frame when making a frame.
 
+** Tabulated List mode
+
++++
+** New user options for tabulated list sort indicators.
+You can now customize which sorting indicator character to display
+near the current column in Tabulated Lists (see variables
+'tabulated-list-gui-sort-indicator-asc',
+'tabulated-list-gui-sort-indicator-desc',
+'tabulated-list-tty-sort-indicator-asc', and
+'tabulated-list-tty-sort-indicator-desc').
+
 
 * New Modes and Packages in Emacs 27.1