types: Split aligned and packed guids

On ia64 alignment requirements are strict. When we pass a pointer to
UUID it needs to be at least 4-byte aligned or EFI will crash.
On the other hand in device path there is no padding for UUID, so we
need 2 types in one formor another. Make 4-byte aligned and unaligned types

The code is structured in a way to accept unaligned inputs
in most cases and supply 4-byte aligned outputs.

Efiemu case is a bit ugly because there inputs and outputs are
reversed and so we need careful casts to account for this
inversion.

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/loader/i386/xnu.c

@@ -694,7 +694,7 @@ grub_cpu_xnu_fill_devicetree (grub_uint64_t *fsbfreq_out)
     {
       void *ptr;
       struct grub_xnu_devtree_key *curkey;
-      grub_guid_t guid;
+      grub_packed_guid_t guid;
       char guidbuf[64];
 
       /* Retrieve current key. */