need support for gpt partition tables

Fix committed in revision 213.

Juerg just added support to growpart to use 'sgdisk'.
The remaining step here is to make cloud-initramfs-growpart to include 'sgdisk'.
That would allow GPT resizing from the initramfs.

There are 2 reasons not to "just do that":
a.) it changes initramfs size dramatically:
$ ls -l /boot/initrd.img*
-rw-r--r-- 1 root root 14936523 Feb 4 17:19 /boot/initrd.img-3.8.0-2-generic
-rw-r--r-- 1 root root 6047018 Feb 4 17:10 /boot/initrd.img-3.8.0-2-generic.dist
b.) As I've described on a thread at http://www.gossamer-threads.com/lists/openstack/dev/23573 , this is actually no longer required to be in the initramfs at all.

bug 1096999 is there to request the function into util-linux for partx and resizepart command.

I've just manually tested on raring, and the following seems to work the whole way through, when having installed psusi's branch at https://code.launchpad.net/~psusi/ubuntu/raring/util-linux/cherry-pick-resize and the new growpart with gpt partition support.

$ img=/tmp/my.img
$ mp=/tmp/mp
$ size=800M
$ osize="400M"
$ sudo rm -f $img; sudo rm -Rf $mp; sudo mkdir $mp

## create a new image $osize big
$ sudo truncate --size $osize "$img"

## add a single GPT partition that takes up the whole image
$ sudo sgdisk --new 1:2048: "$img"

## grow the image (as a hypervisor would do)
$ sudo truncate --size $size $img

## attach the image to a device
$ lodev=$(sudo losetup --show --find "$img")
$ echo $lodev
/dev/loop0

## put a filesystem on it, mount it, then grow the partition
$ sudo mkfs.ext4 ${lodev}p1
$ sudo mount ${lodev}p1 "$mp"
$ sudo growpart ${lodev} 1

## /proc/partitions still has old information

## tell kernel about grown partition
$ sudo partx --update 1 ${lodev}

## /proc/partitions has new information

## filesystem can now be re-sized
$ sudo resize2fs ${lodev}p1

At the moment, I'm thinking that growpart should actually just grow the ability to invoke partx. There isn't any reason why cloud-init or some other tool should have to know about this other than possibly knowing to pass a new flag to growpart.

The other path would be to have cloud-init know that it should invoke growpart and then to invoke partx, but that seems unnecessary.

This bug was fixed in the package cloud-utils - 0.26-0ubuntu2

---------------
cloud-utils (0.26-0ubuntu2) raring; urgency=low

  * debian/copyright: fix formatting
  * sync to trunk at revno 216
    * support for GPT partitions in growpart via sgdisk (LP: #1087526)
    * depend on wget and ca-certificates for ubuntu-cloudimg-query
      (LP: #1062671)
    * fix sfdisk parsing (LP: #1007415)
 -- Scott Moser <email address hidden> Mon, 04 Feb 2013 15:18:49 -0500

fixed in 0.28