now by default, FLUSH, OPTIMIZE, ANALYZE, REPAIR commands are written to the
binlog, unless the new NO_WRITE_TO_BINLOG keyword was used :
OPTIMIZE NO_WRITE_TO_BINLOG table t;

Previously these commands were never written to the binlog, but there are
2 reasons to change this :
- the RENAME TABLE in MERGE table bug (#175) on slave
- the possible "differently optimised queries may lead to different
updates on the master and slave" bug, until we have automatic ORDER BY.

FLUSH LOGS/SLAVE/MASTER/TABLES WITH READ LOCK are never written to the binlog.
New test for the new logging behaviour.
Other small change : reload_acl_and_cache() and reset_slave() don't send their errors themselves,
this is more usual.