able to vsync when writing to video memory

```
seems hitchhikr realized perfect vsync for lcd/tv out.
maybe we need to include this function in sdk?

details here:
http://boards.dingoonity.org/dingoo-development/dingear-v1-0/
```

Original issue reported on code.google.com by `djd...@gmail.com` on 23 Dec 2010 at 12:04
