empty binlog files appear in data directory

[Seppo Jaakola]

If RBR level binlogging is enabled, mysqld does not write replication events to the binlog files.
wsrep catches the events and replicates before the write to binlog file would happen.

This should be changed so that binlog files are appended in same way as with native mysqld.
Also, it seems that there should be new option variable for telling if wsrep should replicate on
SQL or RBR level (wsrep_replication_level or something).

[Seppo Jaakola (seppo-jaakola)]

There was a bug in binlog event management for autocommit queries. STMT_END_F was not set.
Modified MYSQL_LOG::is_open() to return true, if wsrep emulates binlog usage (and not writing to real file).
This enables control to pass to THD::binlog_query(), where flag will be set correctly.