Bug#1131925: Include argon2

[Steven Maddox]

Package: grub-efi-amd64-signed

Can we include argon2 support in this package please?  It is in the 
-unsigned version of this package already (and that works fine).

With 2.14 now properly (and FINALLY) supporting LUKS2 and argon2 we can 
now have a fully encrypted root filesystems (with /boot included) and 
just 1 other partition - the EFI partition itself.

I'm not massively a fan of MS's lead on Secure Boot... but it's a 
fixture that isn't going anywhere and allowing regular people to use it 
with full disk encryption and GRUB would be a brilliant thing to have.

Yes I know what a UKI is... don't want it... I like my GRUB :)