Bug#607642: More info for #607642

[Paul Brook]

Further investigation shows that it's actually the use of GUID partition 
tables that cause confusion. grub-probe correctly identifies filesystem and 
LVM device, but fails to map partitions for the constituent devices.

The lack of GUID partition table support is not directly relevant to this bug. 
I'm sure there are other partitioning schemes that grub does not understand.

Paul