startup: show the helpful message only when ^G has not been rebound

(Well, it now checks that ^G is still the first shortcut that is bound
to 'do_help', but that is good enough: if the user did any rebinding,
they probably do not need any reminder about how to invoke 'Help'.)

This fixes https://savannah.gnu.org/bugs/?60315.
Reported-by: Robert Goulding <goulding.2@nd.edu>

src/nano.c

@@ -2502,11 +2502,16 @@ int main(int argc, char **argv)
 #ifdef ENABLE_NANORC
 	if (startup_problem != NULL)
 		statusline(ALERT, startup_problem);
+
+#define NOTREBOUND  first_sc_for(MMAIN, do_help) && \
+						first_sc_for(MMAIN, do_help)->keycode == 0x07
+#else
+#define NOTREBOUND  TRUE
 #endif
 
 #ifdef ENABLE_HELP
 	if (*openfile->filename == '\0' && openfile->totsize == 0 &&
-				openfile->next == openfile && !ISSET(NO_HELP))
+				openfile->next == openfile && !ISSET(NO_HELP) && NOTREBOUND)
 		statusbar(_("Welcome to nano.  For basic help, type Ctrl+G."));
 #endif