Signed integer format specifier forced to print the binlog header with server_id
negative if the unsigned value sets the sign-bit ON.
  
Fixed with correcting the specifier to correspond to typeof(server_id) == ulong.

mysql-test/r/mysqlbinlog.result:
  results changed.
mysql-test/t/mysqlbinlog.test:
  displaying the expected unsignedly formatted server_id value, bug#37313.
sql/log_event.cc:
  Format specifier is corrected to correspond to typeof(server_id).