fix for Valgrind errors: query_id needs to be inited early (already fixed in 5.0 by Konstantin) and so does client_capabilities (not fixed in 5.0);
because they are used by net_printf() and push_warning(), which can be called if check_connection() fails.


sql/mysqld.cc:
  not needed anymore
sql/repl_failsafe.cc:
  not needed anymore
sql/slave.cc:
  not needed anymore
sql/sql_class.cc:
  query_id needs to be inited early (already fixed in 5.0 by Konstantin) and so does client_capabilities (not fixed in 5.0);
  because they are used by net_printf() and push_warning(), which may be called if check_connection() fails.