rpc: add a busy_syncing field to get_info

true if and pretty much only if new blocks are being added

src/cryptonote_protocol/cryptonote_protocol_handler.h

@@ -117,6 +117,8 @@ namespace cryptonote
     std::string get_peers_overview() const;
     std::pair<uint32_t, uint32_t> get_next_needed_pruning_stripe() const;
     bool needs_new_sync_connections() const;
+    bool is_busy_syncing();
+
   private:
     //----------------- commands handlers ----------------------------------------------
     int handle_notify_new_block(int command, NOTIFY_NEW_BLOCK::request& arg, cryptonote_connection_context& context);