rcfile: rename bindable function 'suspendenable' to 'suspendable'

The name of a toggle function should match the name of the corresponding
option, like for 'mouse' and 'linenumbers' and 'smarthome' and such.

doc/nano.texi

@@ -1406,7 +1406,7 @@ Refreshes the screen.
 
 @item suspend
 Suspends the editor (if the suspending function is enabled, see the
-"suspendenable" entry below).
+@code{suspendable} toggle item below).
 
 @item casesens
 Toggles whether searching/replacing ignores or respects the case of
@@ -1517,9 +1517,10 @@ Toggles whether typed tabs will be converted to spaces.
 @item mouse
 Toggles mouse support.
 
-@item suspendenable
+@item suspendable
 Toggles whether the suspend keystroke (@kbd{^Z} by default)
 will actually suspend the editor.
+(The old name of this function, 'suspendenable', is deprecated.)
 
 @end table
 

doc/nanorc.5

@@ -727,7 +727,7 @@ Refreshes the screen.
 .TP
 .B suspend
 Suspends the editor (if the suspending function is enabled, see the
-"suspendenable" entry below).
+\fBsuspendable\fR toggle item below).
 .TP
 .B casesens
 Toggles whether searching/replacing ignores or respects the case of
@@ -838,9 +838,10 @@ Toggles whether typed tabs will be converted to spaces.
 .B mouse
 Toggles mouse support.
 .TP
-.B suspendenable
+.B suspendable
 Toggles whether the suspend keystroke (\fB^Z\fR by default)
 will actually suspend the editor.
+(The old name of this function, 'suspendenable', is deprecated.)
 .RE
 
 .TP

src/rcfile.c

@@ -466,7 +466,8 @@ keystruct *strtosc(const char *input)
 		else if (!strcmp(input, "mouse"))
 			s->toggle = USE_MOUSE;
 #endif
-		else if (!strcmp(input, "suspendenable"))
+		else if (!strcmp(input, "suspendable") ||
+		         !strcmp(input, "suspendenable"))  /* Deprecated; remove in 2022. */
 			s->toggle = SUSPENDABLE;
 		else
 #endif /* !NANO_TINY */