add readme.

lichao

2021-06-07 2c73aac1fe62495d8c863a92a34d191cf8e87fc0

 src/shm_msg_queue.h

@@ -29,7 +29,7 @@
{
public:
   typedef int64_t RawData;
   typedef ShmObject<SharedQ63> Shmq;
   typedef NamedShmObject<SharedQ63> Shmq;
   typedef Shmq::Data Queue;
   typedef Shmq::ShmType ShmType;
   typedef uint64_t MQId;