For example the Binlog_dump thread (on the master) sometimes showed "Slave:".
And there were confusing messages where "binlog" was employed instead
of "relay log".


sql/log.cc:
  MYSQL_LOG::wait_for_update() is used by the binlog_dump and I/Oslave threads,
  and it updates thd->proc_info, so we need a bool to not show the same
  proc_info for 2 different things (previously we showed "Slave: etc" and that's
  bad for a binlog_dump thread).
sql/slave.cc:
  Clearer thd-proc_info for slave threads.
sql/sql_class.h:
  prototype change
sql/sql_repl.cc:
  clearer thd->proc_info for binlog_dump thread