New package: gdisk

This includes two separately configurable parition manipulation
utilities: gdsik and sgdisk are to GPT disks what fdisk and sfdisk are
in MBR land.

[Peter: patch source, fix typos, fix partial build, pass correct flags]
Signed-off-by: Malte Starostik <m-starostik@versanet.de>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>