use char instead of uint8_t, fix compiler warnings so toxic compiles with -Wall and -Werror on gcc and clang

src/help.c

@@ -105,6 +105,8 @@ static void help_draw_bottom_menu(WINDOW *win)
 {
     int y2, x2;
     getmaxyx(win, y2, x2);
+    (void) x2;
+
     wmove(win, y2 - 2, 1);
 
     wattron(win, A_BOLD | COLOR_PAIR(BLUE));