Patch by Ian Good for MDEV-4319: mysqlbinlog output ambiguous escaping
Patch by Ian Good for MDEV-4319: mysqlbinlog output ambiguous escaping

The output of mysqlbinlog (with "-v --base64-output=DECODE-ROWS" flags) can not always be read or parsed correctly
when string columns contain single-quotes or backslash characters.

The fix for this bug is to escape single-quote and backslash characters on output, so that the result is both more
readable and more easily parse-able.

Note that this is just for comments, so it doesn't affect the replication.

sql/log_event.cc:
  Escape \ and ' properly for mysqlbin user comments.

ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,ollie314/server,davidl-zend/zenddbi,flynn1973/mariadb-aix,davidl-zend/zenddbi,ollie314/server,ollie314/server,flynn1973/mariadb-aix,slanterns/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,ollie314/server,natsys/mariadb_10.2