More work on diff xmit, not finished yet

luprex/core/cpp/util.hpp

@@ -21,6 +21,7 @@ enum WorldType {
 using stringvec = std::vector<std::string>;
 using stringset = std::set<std::string>;
 using HashValue = std::pair<uint64_t, uint64_t>;
+using IdVector = std::vector<int64_t>;
 
 // Split a string into multiple strings
 stringvec split(const std::string &s, char sep);