xenopsd: backend interface changes in preparation for the new xenlight backend

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xenopsd: add initial version of a backend based on libxenlight

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xenopsd: xenlight: use Event module in async handling

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xenlight: add xenlight.xentoollog build dependency

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Merge pull request #17 from robhoes/xenlight4

Adding the Xenlight backend!