Support skipping to the start and end

zig/sdl/hello_sdl.zig

    var quit = false;
    var skip: i32 = 0;
    var num_lines: i32 = 0;
    while (!quit) {
        var event: c.SDL_Event = undefined;
        while (c.SDL_PollEvent(&event) != 0) {
                                }
                                msg[max_chars] = 0;
                                pos = 0;
                                num_lines = 0;
                                var lines = std.mem.split(result, "\n");
                                var line = lines.next();
                                while (line != null) : (line = lines.next()) {
                                    num_lines += 1;
                                }
                            },
                            c.SDLK_UP => {
                                if (skip > 0) {
                            c.SDLK_PAGEDOWN => {
                                skip += 10;
                            },
                            c.SDLK_HOME => {
                                skip = 0;
                            },
                            c.SDLK_END => {
                                if (num_lines > 10) {
                                    skip = num_lines - 10;
                                }
                            },
                            else => {},
                        }
                    }