Address review comments

 Rule of five: add destructor
 Add a note to COMMIT.md for 3rd party json.

include/rocksdb/transaction_log.h

@@ -59,9 +59,15 @@ struct BatchResult {
     SequenceNumber sequence = 0;
     std::unique_ptr<WriteBatch> writeBatchPtr;
 
+    // Add empty __ctor and __dtor for the rule of five
+    // However, preserve the original semantics and prohibit copying
+    // as the unique_ptr member does not copy.
     BatchResult() {
     }
 
+    ~BatchResult() {
+    }
+
     BatchResult(const BatchResult&) = delete;
 
     BatchResult& operator=(const BatchResult&) = delete;

third-party/fbson/COMMIT.md

 fbson commit: 
 https://github.com/facebook/mysql-5.6/commit/55ef9ff25c934659a70b4094e9b406c48e9dd43d
+
+# TODO.
+* Had to convert zero sized array to [1] sized arrays due to the fact that MS Compiler complains about it not being standard. At some point need to contribute this change back to MySql where this code was taken from.