Using new lttng tracepoint API

Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>
Export required symbols from lttng-tracepoint

Addons modules register tracepoints, and the register/unregister functions
needs to be exported for linux >= 3.15.

Signed-off-by: Francis Giraldeau <francis.giraldeau@gmail.com>
Add virtual machine UID to the event payload

This allows to uniquely identify which machines are involved in the exchange

Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>