Update dropbear to version 2015.71, released on 3 Dec 2015.
Refresh patches.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

SVN-Revision: 48243

This enables passworldless login for root via SSH whenever no root
password is set (e.g. after reset, flashing without keeping config
or in failsafe) and removes telnet support alltogether.

Signed-off-by: Steven Barth <steven@midlink.org>

SVN-Revision: 46809