message: Update chain_plugin.hpp
  Making ``core_symbol`` and ``core_symbol_precision`` optional
diff: @@ -97,8 +97,8 @@ public:
  //string recent_slots;
  //double participation_rate = 0;
  optional<string> server_version_string;
  - string core_symbol;
  - uint64_t core_symbol_precision;
  + optional<string> core_symbol;
  + optional<uint64_t> core_symbol_precision;
  };
  get_info_results get_info(const get_info_params&) const;
  