add isReading() to Channel.h
add isReading() to Channel.h

zhuangshi23/muduo,zhuangshi23/muduo,zouzl/muduo-learning,westfly/muduo,zhuangshi23/muduo,westfly/muduo,zxylvlp/muduo,zxylvlp/muduo,zxylvlp/muduo,zouzl/muduo-learning,zouzl/muduo-learning,westfly/muduo