sun: initialize basic partition table fields

sun: initialize basic partition table fields

libparted completely ignores basic fields (version, nparts and sanity)
in the sun VTOC, then for example fdisk prints warnings for such
partition table:

	# fdisk -lu /dev/sdb
	Detected sun disklabel with wrong version [0x00000000].
	Detected sun disklabel with wrong sanity [0x00000000].
	Detected sun disklabel with wrong num_partitions [0].

It seems that the current libparted sun support follows old Linux
kernel code, but the code was changed 3 years ago (see kernel commit
3961bae0ac030a70ae2e0578270203889021f1a1).

Note that the number of partitions (nparts) is optional for Linux
kernel, but fdisk(8) strictly requires SUN_DISK_MAXPARTITIONS (=8)
there. This patch sets nparts to SUN_DISK_MAXPARTITIONS rather then
use a real number of partitions.

* NEWS (Bug fixes): Mention it.
* libparted/labels/sun.c: Update from kernel.
* tests/t4001-sun-vtoc.sh: New file.  Test for this.