ref: 2f5ecec958a91df3eaa14e7be590a8eb800cb28f
parent: 9ed97c73627482b975992b20a53d9fca426f8cbb
author: xiaotiansf <xiaotianshimail@gmail.com>
date: Tue Oct 15 18:23:34 EDT 2019
re-structure SWelsDecoderContext and others and prepare for the support of multi-threading support.