Binlogrouter does not support binlog_checksum=NONE

If the server from where the binlog events are being replicated does not have binlog checksums enabled, the binlogrouter will corrupt the last four bytes of all events will report an error. This happens because it assumes that checksums are always included in the replication stream.

The binlogrouter should support replication without checksums but given the fact that by default replication uses checksums, the importance of supporting this is not known. For the sake of completeness, it should still be supported by the router.