Version 2.3.0-rc1

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fix: doc/examples VPATH build

Fixes #577

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Merge branch 'master' of git://git.lttng.org/lttng-ust