RCU dereference check if within read-side critical section

Need to link with liburcu-common in addition to urcu flavor.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Print error rather than abort

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Detect unbalanced lock/unlock

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>