bindings: add easier keystrokes for the linenumber and softwrap toggles

For most people, M-N and M-S are simpler to type than M-# and M-$,
and more mnemonic.

doc/nano.texi

@@ -640,12 +640,18 @@ The following global toggles are available:
 @item Mouse Support
 @kbd{Meta-M} toggles the @option{-m} (@option{--mouse}) command-line option.
 
+@item Line Numbers
+@kbd{Meta-N} toggles the @option{-l} (@option{--linenumbers}) command-line option.
+
 @item Tabs To Spaces
 @kbd{Meta-O} toggles the @option{-E} (@option{--tabstospaces}) command-line option.
 
 @item Whitespace Display
 @kbd{Meta-P} toggles the displaying of whitespace (@pxref{Whitespace}).
 
+@item Soft Wrapping
+@kbd{Meta-S} toggles the @option{-$} (@option{--softwrap}) command-line option.
+
 @item Expert/No Help
 @kbd{Meta-X} toggles the @option{-x} (@option{--nohelp}) command-line option.
 
@@ -656,12 +662,6 @@ The following global toggles are available:
 @item Suspension
 @kbd{Meta-Z} toggles the @option{-z} (@option{--suspend}) command-line option.
 
-@item Line Numbers
-@kbd{Meta-#} toggles the @option{-l} (@option{--linenumbers}) command-line option.
-
-@item Soft Wrapping
-@kbd{Meta-$} toggles the @option{-$} (@option{--softwrap}) command-line option.
-
 @end table
 
 

src/global.c

@@ -1256,8 +1256,10 @@ void shortcut_init(void)
 	/* Group of "Appearance" toggles. */
 	add_to_sclist(MMAIN, "M-X", 0, do_toggle_void, NO_HELP);
 	add_to_sclist(MMAIN, "M-C", 0, do_toggle_void, CONSTANT_SHOW);
+	add_to_sclist(MMAIN, "M-S", 0, do_toggle_void, SOFTWRAP);
 	add_to_sclist(MMAIN, "M-$", 0, do_toggle_void, SOFTWRAP);
 #ifdef ENABLE_LINENUMBERS
+	add_to_sclist(MMAIN, "M-N", 0, do_toggle_void, LINE_NUMBERS);
 	add_to_sclist(MMAIN, "M-#", 0, do_toggle_void, LINE_NUMBERS);
 #endif
 	add_to_sclist(MMAIN, "M-P", 0, do_toggle_void, WHITESPACE_DISPLAY);