There are 3 implementations of a GUID in GRUB. Replace them with
a common one, placed in types.h.
It uses the "packed" flavor of the GUID structs, the alignment attribute
is dropped, since it is not required.
Signed-off-by: Oliver Steffen <osteffen@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>