libfdisk: fix script parser, add debug messages

Signed-off-by: Karel Zak <kzak@redhat.com>
fdisk: add support for sfdisk scripts

New commands 'I' and 'O' allows to read and write sfdisk compatible
scripts by fdisk. It means that you can save your work (partition
table) and later use it (in fdisk, sfdisk or cfdisk) to create a new
partition table.

Signed-off-by: Karel Zak <kzak@redhat.com>
cfdisk: add support for sfdisk scripts

Signed-off-by: Karel Zak <kzak@redhat.com>