* fhandler_console.cc (beep): Use a more Windows-generic wav file if the beep
is missing. Use a more foolproof way to find out whether we should be
recreating the missing key.
* registry.h (reg_key::_disposition): New field.
(reg_key::created): New function.
* registry.cc (reg_key::reg_key): Set _disposition to zero by default.
(reg_key::build_key): Fill in _disposition field.