tracepoints: use tracepoint() directly for tracing

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
core: add basic code for a multiple-producer ring

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: add logic for using a multiple-producer ring

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: add method to publish message in worker

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
tests: add some unit tests for fast ring

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>