Log Message:
update to 0.50
changes:
- Add DROPBEAR_PASSWORD environment variable to specify a dbclient password
- Use /dev/urandom by default, since that's what everyone does anyway
- Exit with an exit code of 1 if dropbear can't bind to any ports
- Improve network performance and add a -W <receive_window> argument for
  adjusting the tradeoff between network performance and memory consumption
- Fix a problem where reply packets could be sent during key exchange,
  in violation of the SSH spec. This could manifest itself with connections
  being terminated after 8 hours with new TCP-forward connections being
  established
- Add -K <keepalive_time> argument, ensuring that data is transmitted
  over the connection at least every N seconds
- dropbearkey will no longer generate DSS keys of sizes other than 1024
  bits, as required by the DSS specification. (Other sizes are still
  accepted for use to provide backwards compatibility)