binlog_streamer: wait indefinitely on logfile rotation

Sometimes, it takes a while for MySQL to create the new binlog file.
So, it's better to wait indefinitely for it. Also, wait only if it's
actually a file not found error.
rowcache: invalidation stats label counts->tables
rowcache_invalidator: improved handling of unknown statements

Changed the invalidator to treat a DML as a DDL if it can recognize the
table name. This is slightly aggressive, but will raise less alarms.
It's a good trade-off since unrecognized DMLs must be rare.
sqlparser: drop obsolete GetDBName
Merge branch 'rowcache'