libparted: use ext_range to find out largest possible partition

libparted: use ext_range to find out largest possible partition

Parted uses /sys/block/DEV/range file to find out how many partitions
can the blockdevice hold and uses this number in its algorithm
for informing the kernel about modified partitions. This works
fine for most devices, however, it fails on partitionable MD arrays,
because these have 1 in range file. Using ext_range should be safer
and work for all devices.

* libparted/arch/linux.c (_device_get_partition_range): Use
/sys/block/DEV/ext_range instead of range sysfs file
* NEWS: Mention the change.

Addresses: http://bugzilla.novell.com/567652