Improve devmapper support

	Improve devmapper support

	* grub-core/kern/emu/getroot.c (grub_util_is_dmraid): Removed.
	(grub_util_is_lvm): New function.
	(grub_util_get_dev_abstraction): Assume dmraid if not lvm rather
	than lvm if not dmraid.
	Handle mapped md nodes.
	* grub-core/kern/emu/hostdisk.c (device_is_mapped): Rename to ...
	(grub_util_device_is_mapped): ... this. Make always available. All users
	updated.
	(grub_util_get_dm_node_linear_info) [HAVE_DEVICE_MAPPER]: New function.
	(convert_system_partition_to_system_disk): Handle lvm, mpath and
	dmraid nodes.
	* include/grub/emu/misc.h (grub_util_device_is_mapped): New proto.

	Also-By: Colin Watson <cjwatson@ubuntu.com>