removed wrongly introduced strlen calls


sql/events.cc:
  removed wrongly introduced strlen calls
sql/mysql_priv.h:
  removed wrongly introduced strlen calls
sql/repl_failsafe.cc:
  removed wrongly introduced strlen calls
sql/sql_db.cc:
  removed wrongly introduced strlen calls
sql/sql_parse.cc:
  removed wrongly introduced strlen calls
sql/sql_show.cc:
  removed wrongly introduced strlen calls