[PATCHv4 0/8] tools: rework VM Generation ID

[David Vrabel <david.vrabel@citrix.com>]

This series reworks the VM Generation ID to a) conform to the
published spec from Microsoft; b) simplify the save/restore code; and
c) extend the libxl API to allow toolstacks to use this feature.

The VM Generation ID must be regenerated with a new random ID after
certain VM operations. Since xl lacks infrastructure for tracking the
life-cycle of snapshots and clones (etc), the safe option of always
using a new generation ID is used.

You can download the spec from:

  http://www.microsoft.com/en-us/download/details.aspx?id=30707

Patch status ([A]cked, [M]odified, [N]ew):

A [1/8] docs: update docs for the ~/platform/generation-id key
A [2/8] hvm: add HVM_PARAM_VM_GENERATION_ID_ADDR
N [3/8] libxc: allow xc_get/set_hvm_param() to get/set 64-bit
N [4/8] libxl: const-ify libxl_uuid_*() API
A [5/8] hvmloader: add helper functions to get/set HVM params
A [6/8] libxc,libxl,hvmloader: strip out outdated VM generation
M [7/8] libxl: allow a generation ID to be specified at domain
A [8/8] xl: generate a new random VM generation ID if requested

Changes in v4:

- Allow xc_get/get_hvm_params() to get/set 64-bit values.
- Const-ify libxl_uuid_*() calls.
- Minor tweaks to libxl internals (gc as param, use GCSPRINTF()).

Changes in v3:

- Specify generation ID in libxl_domain_build_info instead of having
  to call a function to set it.
- Improve docs.

Changes in v2:

- Use libxl_uuid for the generation ID.
- Add "generation_id" option to xl domain configuration file and use
  this to set a random generation ID every time.

David