Add grub-probe support for NetBSD.

	Add grub-probe support for NetBSD.

	* util/getroot.c (find_root_device): Convert block device to
	character device on NetBSD.
	* util/probe.c (probe): Require character device on NetBSD.
	* util/hostdisk.c: NetBSD specific headers.
	(configure_device_driver): new function to tune device driver
	parameters (currently only for NetBSD floppy driver).
	(grub_util_biosdisk_open): NetBSD specific code (get disk size
	via disklabel ioctl).
	(open_device): call configure_device_driver on NetBSD.
	(convert_system_partition_to_system_disk): NetBSD specific code.
	(device_is_wholedisk): Likewise.
	(grub_util_biosdisk_get_grub_dev): Likewise.
	(make_device_name): Fixed a typo in bsd_part_str.
	* configure.ac: check for opendisk() and getrawpartition() on
	NetBSD and set LIBUTIL.
	* Makefile.in: add LIBUTIL to LIBS.