nano: enable showing line numbers with M-N (Alt-n)

Backport new upstream patch to enable toggling the display of
the line numbers with the shortcut key M-N (Alt-n).

Also the cmdline option "-l" works.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

utils/nano/patches/0001-bindings-allow-toggling-line-numbers-when-enabled-al.patch

@@ -0,0 +1,48 @@
+From 3a94a0bb89363ef8768546973aab051cd5bf4622 Mon Sep 17 00:00:00 2001
+From: Benno Schulenberg <bensberg@telfort.nl>
+Date: Wed, 10 Nov 2021 09:20:56 +0100
+Subject: [PATCH] bindings: allow toggling line numbers (when enabled) also in
+ tiny version
+
+As a special case, and because it doesn't need any feedback on the
+status bar nor other calls, add a special function and key binding
+to allow the user to flip the LINE_NUMBERS flag also in a tiny nano.
+
+This fixes https://savannah.gnu.org/bugs/?61441.
+Reported-by: Hannu Nyman <hannu.nyman@iki.fi>
+---
+ src/global.c | 14 +++++++++++++-
+ 1 file changed, 13 insertions(+), 1 deletion(-)
+
+--- a/src/global.c
++++ b/src/global.c
+@@ -554,6 +554,14 @@ functionptrtype interpret(int *keycode)
+ }
+ #endif /* ENABLE_BROWSER || ENABLE_HELP */
+ 
++#if defined(NANO_TINY) && defined(ENABLE_LINENUMBERS)
++/* Allow toggling line numbers (when enabled) also in the tiny version. */
++void toggle_numbers(void)
++{
++	TOGGLE(LINE_NUMBERS);
++}
++#endif
++
+ /* These two tags are used elsewhere too, so they are global. */
+ /* TRANSLATORS: Try to keep the next two strings at most 10 characters. */
+ const char *exit_tag = N_("Exit");
+@@ -1250,9 +1258,13 @@ void shortcut_init(void)
+ 	add_to_sclist(MMAIN|MBROWSER|MHELP, "M-W", 0, do_findnext, 0);
+ 	add_to_sclist(MMAIN|MBROWSER|MHELP, "M-Q", 0, do_findprevious, 0);
+ #ifdef NANO_TINY
++#ifdef ENABLE_LINENUMBERS
++	add_to_sclist(MMAIN, "M-N", 0, toggle_numbers, 0);
++#else
+ 	add_to_sclist(MMAIN, "M-B", 0, to_prev_word, 0);
+-	add_to_sclist(MMAIN, "M-D", 0, to_prev_word, 0);
+ 	add_to_sclist(MMAIN, "M-N", 0, to_next_word, 0);
++#endif
++	add_to_sclist(MMAIN, "M-D", 0, to_prev_word, 0);
+ 	add_to_sclist(MMAIN, "M-F", 0, to_next_word, 0);
+ #else
+ 	add_to_sclist(MMAIN, "M-]", 0, do_find_bracket, 0);