ref: fc56c7d007762e4dc95e04517cc19326329e1eae
parent: 99412b0fc228beb56efaaaad25e3b6b543dbb519
author: Licai Guo <guolicai@gmail.com>
date: Wed Jan 22 19:07:21 EST 2014
1. use WELS_CLIP1 to replace table look-up; 2. fix bugs about buffer overflow 3. add more boundary checks