Add simple async based XenAPI event example

Signed-off-by: David Scott <dave.scott@citrix.com>
Regenerate OASIS

Signed-off-by: David Scott <dave.scott@citrix.com>
Build a local replica of the metadata from the event stream

Signed-off-by: David Scott <dave.scott@citrix.com>
event example: check the local replica matches the remote

Signed-off-by: David Scott <dave.scott@citrix.com>
event example: run 2 threads in parallel

Signed-off-by: David Scott <dave.scott@citrix.com>
Update CHANGES

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #16 from djs55/event-test

Add async event test