grub 2.00: Bugfix for CVE-2015-8370

grub 2.00: Bugfix for CVE-2015-8370

See: http://hmarco.org/bugs/CVE-2015-8370-Grub2-authentication-bypass.html

"A vulnerability in Grub2 has been found. Versions from 1.98 (December, 2009)
to 2.02 (December, 2015) are affected. The vulnerability can be exploited
under certain circumstances, allowing local attackers to bypass any kind of
authentication (plain or hashed passwords). And so, the attacker may take
control of the computer."

Signed-off-by: Matthias Fischer <matthias.fischer@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>